Behind The Names The Botany Of Tea Tree Cajuput And Niaouli

LYN A.CRAVEN

Australian National Herbarium, CSIRO Division of Plant Industry, Canberra, Australia

INTRODUCTION

"We know what plant X is. Why should we have to worry about its scientific name?" Well, sometimes calling a plant X is neither sufficiently precise to enable us to communicate unambiguously nor to find the information that we seek in the ever-burgeoning literature with which we must cope. Australians use the name tea tree to refer to many indigenous species of Leptospermum, Melaleuca and Neofabricia (Wrigley and Fagg 1993). These three genera belong to the family Myrtaceae so they do have something in common. Clearly though, the use of tea tree by itself will not suffice as the only name for the subject of this book and we must use its scientific name, Melaleuca alternifolia, to distinguish it unambiguously from all the other tea trees.

Apart from being a label, the scientific name of a plant can be considered a concise definition as to what the plant actually is, as the name can be related to a particular morphological circumscription. Similarly with the many ecological and chemical attributes that species possess. Melaleuca leucadendra sensu Bentham taxonomically, and ecologically, geographically and chemically, is very different to M. leucadendra sensu Blake. Unless the name is qualified such as in the previous sentence, it is not easy to determine which of the potentially several taxonomic concepts a particular author is using.

In itself a name is not especially useful as an indication to the position occupied by a species in taxonomic classifications, other than informing us of the genus to which the species belongs. The binomial nomenclatural system, i.e. the combination of a generic with a specific epithet (such as Melaleuca alternifolia), does not cater for taxa between the ranks of genus and species, such as section or series. This is unfortunate in large genera such as Melaleuca in which we need to know in which part of the genus our taxon or taxa of interest are classified. Notwithstanding this, the scientific name is our only sure password to the information that is available in the literature.

This contribution provides a brief outline of the genus Melaleuca and of the species groups to which tea tree, cajuput and niaouli belong.

THE GENUS MELALEUCA

Melaleuca was established as a genus by Linnaeus in 1767 with M. leucadendra as its only, and hence type, species. Linnaeus based his genus on the pre-Linnaean Arbor alba that was described by Rumphius from plants growing on Ambon in present day Indonesia (Rumphius

1741). From 1767 until the mid-1800s, several further species were added to the genus but it was not until 1867 that the first comprehensive treatment of Melaleuca was published in Bentham's account of Myrtaceae in his classic flora of Australia, Flora Australiensis (Bentham 1867). Within Melaleuca, Bentham recognised 97 species in 7 series. His series include some groupings of undoubtedly closely related species but overall the classification is artificial. This is not a reflection upon the general quality of Bentham's treatment but is an indication of the difficulty inherent in classifying a large group of species that, while differing considerably in gestalt, is remarkably similar in essential structural details. To the present day, Bentham's work has remained the most monographic account of Melaleuca available.

Since 1867, many other species have been described in Melaleuca by botanists. These usually have been published as isolated descriptions of novelties or in accounts of flora collected by large expeditions; it has only been in recent decades that studies of Melaleuca within large regions have been undertaken and published. These more comprehensive studies include a revision of the broad-leaved paperbarks (Blake 1968), a revision of Melaleuca in South Australia (Carrick and Chorney 1979), a treatment of the northern and eastern Australian species (Byrnes 1984, 1985, 1986), treatments of several largely southwestern and eastern Australian species groups (Barlow 1987; Barlow and Cowley 1988; Cowley et al. 1990), and a revisionary level treatment of the New Caledonian species (Dawson 1992). The genus Asteromyrtus, included in Melaleuca by Bentham (1867) and Byrnes (1984, 1985) was resurrected by Craven (1989) to accommodate a constellation of species most of which had been treated under Melaleuca but of which one had been placed in the monotypic genus Sinoga by Blake (1958). Asteromyrtus is not closely related to Melaleuca; its relationships lie with Agonis in the Leptospermum group of genera. In passing it may be noted that at least one species of Asteromyrtus, A. symphyocarpa, has potential as a viable source of essential oil (Chapter 16, this volume). Preparatory work towards an account of Melaleuca for Flora of Australia is in train and a precursory paper enumerating all the Australian species and providing identification keys currently is being completed by L.A.Craven and B.J.Lepschi.

According to the classification of Briggs and Johnson (1979), the genera most closely related to Melaleuca are Callistemon, Conothamnus and Lamarchea while Beaufortia, Calothamnus, Eremaea, Phymatocarpus and Regelia are more distantly related. It seems that there is no especially close relationship with the genera clustered around Leptospermum, i.e. Agonis, Angasomyrtus, Asteromyrtus, Homalospermum, Kunzea, Neofahrma and Pericalymma. The conventional circumscription of Melaleuca given below may require amendment when research in progress by the author into the relationships of Callistemon and Conothamnus to Melaleuca is concluded. At least two species of Australian Callistemon., C. glaucus and C. viminalis, have their stamens grouped into 5 basally fused groups, one of the key generic characters of Melaleuca. Indeed, this was the basis for Byrnes' transfer of the eastern Australian species, C. viminalis, to Melaleuca (Byrnes 1984, 1986). Similarly, the endemic New Caledonian species of Callistemon are very close to the endemic New Caledonian Melaleuca, several of them having stamens fused into groups, and they may be transferred to Melaleuca as a result of research in progress.

As it is presently circumscribed, Melaleuca consists of about 230 species (Craven 1997). The great majority of the species, about 220, is endemic to Australia and Tasmania but several also occur in adjacent parts of Indonesia and Papua New Guinea and one species, M. cajuputi, extends from Australia northwards to the Asian mainland. There is one endemic species in Lord Howe Island, M. howeana, and three species in New Caledonia (eight including the Callistemon species) of which M. quinquenervia also occurs in eastern Australia and New Guinea. Within Myrtaceae, Melaleuca is characterised by possession of the following combination of features: Shrubs or trees; leaves spiral, decussate or ternate, small to medium-sized, the venation pinnate to parallel; flowers in spikes or clusters or sometimes solitary, the basic floral unit being a monad, dyad or triad; sepals 5 (rarely 0); petals 5; hypanthium fused to the ovary in the proximal region only; stamens few to numerous, the filaments fused for part of their length into 5 bundles, the anthers dorsifixed (or rarely basifixed) and versatile with two parallel cells that open via longitudinal slits; ovary 3-celled, the ovules few to numerous; fruit a capsule within an usually woody to subwoody fruiting hypanthium; seeds with a thin testa, generally obovoid-oblong to obovoid, unwinged, the cotyledons planoconvex to obvolute.

TEA TREE

Tea tree, Melaleuca alternifolia (Plates 2, 3), is very closely related to M. linariifolia, and it is not surprising that Maiden and Betche treated the plant as a variety of that species when they described it in 1905. It belongs in the M. linariifolia species group of which there are five currently accepted species: M. alternifolia, M. dissitiflora, M. linariifolia, M. linophylla and M. trichostachya. Maiden & Betche distinguished their variety alternifolia as having alternate leaves that are much narrower and usually shorter than those of M. linariifolia sensu stricto and having its flowers (Plate 3) less densely arranged in the inflorescences. Cheel considered that the differences between the two, taken with their apparent geographic isolation, were sufficient justification for the variety to be raised to specific rank (Cheel 1924).

The first-described, and best known, species of the group is M. linariifolia; this was described by Smith in 1797 from specimens collected in the Sydney region in 1795. M. linariifolia is widely cultivated in Australia as it is hardy and forms an attractive large shrub or small tree with masses of pure white flowers.

The next described species is M. trichostachya, described by Lindley in 1848 from specimens collected by the explorer Thomas Mitchell in 1846 in subtropical Queensland. Bentham, however, reduced M. trichostachya to a variety of M. linariifolia in 1867. Of the recent taxonomists who have worked on Melaleuca, Bentham's placement was followed by Byrnes (1985) but Quinn et al. (1989), who studied the complex in more detail than did Byrnes, recognised M. trichostachya as a distinct species. The remaining two species of the group, M. linophylla and M. dissitiflora, were described in 1862 and 1863, respectively, by the 19th Century Australian botanist, Ferdinand Mueller.

Geographically, the group is widespread and occurs in a correspondingly broad range of climates. The distributions of the species are shown in Figure 1. Given the occurrence of terpinen-4-ol chemotypes in M. alternifolia, M. dissitiflora and M. linariifolia, it would seem that there is scope for a more intensive survey of the M. linariifolia group to gain a greater understanding of the chemotypes and their distributions. Then it would be possible

Figure 1 Distributions of Melaleuca species. 1, M. alternifolia M. dissitiflora V 2, M. linariifolia M. linophylla -V 3, M. trichostachya •

Figure 1 Distributions of Melaleuca species. 1, M. alternifolia M. dissitiflora V 2, M. linariifolia M. linophylla -V 3, M. trichostachya •

to consider the prospects for expanding the tea tree oil industry, presently centred upon M. alternifolia in NE New South Wales, by growing other terpinen-4-ol rich genotypes in regions to which they are suited climatically and edaphically, by introgressing novel genes into M. alternifolia and M. linariifolia for crop improvement with the NE New South Wales region, or by both means.

Morphologically, the species need to be studied further, in the case of the central Australian representatives preferably with flowering and fruiting materials collected from the same trees, so that more comprehensive and possibly more definitive circumscriptions can be made. Until then, the species of the M. linariifolia species group can be distinguished by means of the key given below.

Future systematic studies should not be restricted to morphological aspects. Molecular systematics, based upon comparative studies of DNA, in particular will assist in establishing the evolutionary relationships of the species. Butcher et al. (1995) studied chloroplast DNA (cpDNA) variation in M. alternifolia, M. linariifolia and M. trichostachya and in part their findings were that M. linariifolia and M. trichostachya were readily distinguished on cpDNA

data. They also found that cpDNA data supported an earlier suggestion based upon leaf terpene data (Butcher et al. 1994) that hybridisation may have occurred between M. alternifolia and M. linariifolia in the southern part of the former species' range. Clearly, the incorporation of molecular data into the systematic synthesis will enable us to devise much more accurate and informative classifications than we have been able to do using morphological data alone.

List of species of the M. linariifolia group, including their synonyms and type specimens

1. Melaleuca alternifolia (Maiden & Betche) Cheel, J. Proc. Roy. Soc. New S. Wales 58:195 (1924). Melaleuca linariifolia var. alternifolia Maiden & Betche, Proc. Linn. Soc. New S.Wales 29:742 (1905). Typus: New South Wales: Coffs Harbour to Grafton, Nov. 1903, Maiden andBoorman s.n. (NSW, holo, n.v.).

2. Melaleuca dissitiflora F.Muell., Fragm. 3:153 (1863). Myrtoleucodendron dissitiflorum (F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Typus: Northern Territory: between Bonney River and Mount Morphett, 1862, Stuart s.n. (MEL, holo, iso, n.v.).

3. Melaleuca linariifolia Sm., Trans. Linn. Soc. London, Bot. 3:278 (1797). Myrtoleucodendron linariifolium (Sm.) Kuntze, Revis. gen. pl. 241 (1891). Melaleuca linariifolia var. typica Domin, Biblioth. Bot. 89:456 (1928), nom. inval Typus: New South Wales: 1795, White s.n. (LINN, holo, n.v.).

Metrosideros hyssopifolia Cav., Icon. 4:20, t.336. f.1. (1797). Melaleuca hyssopifolia (Cav.) Dum.Cours., Bot. cult. 2, 5:375 (1811). Typus: The illustration accompanying the original description.

4. Melaleuca linophylla F.Muell., Fragm. 3:115 (1862). Myrtoleucodendron linophyllum (F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Typus: Western Australia: northwest, 1861, Gregory s.n. (MEL, holo, n.v.; BRI, K, iso, n.v.).

5. Melaleuca trichostachya Lindl., in Mitchell, J. exped. trop. Australia 277 (1848). Melaleuca linariifolia var. trichostachya (Lindl.) Benth., Fl. Austral. 3:141 (1867). Myrtoleucodendron trichostachyum (Lindl.) Kuntze, Revis. gen. pl. 242 (1891). Typus: Queensland: sandy bed of Belyando River, 16 Aug. 1846, Mitchell 224 (CGE, holo, n.v.; K, MEL, NSW, iso, n.v.).

Key to the species of the M. linariifolia group

1. Leaves decussate

2. Ovules 85-120 per locule; capsule persisting within the fruiting hypanthium; cotyledons planoconvex M. linariifolia

2. Ovules 25-45 per locule; capsule at length deciduous and the empty fruiting hypanthium then persisting; cotyledons obvolute to almost planoconvex

M. trichostachya

1. Leaves spiral

3. Hypanthium glabrous or effectively so (if distinctly hairy, then stamens more than 12mm long)

4. Stamens up to 12mm long; capsule at length deciduous and the empty fruiting hypanthium then persisting M. trichostachya

4. Stamens more than 12mm long; capsule persisting within the fruiting hypanthium M. alternifolia

3. Hypanthium distinctly hairy

5. Stamens 2.2-3.5mm long, 7-15 per bundle M. linophylla

5. Stamens 4mm or more long, 15-35 per bundle M. dissitiflora

CAJUPUT AND NIAOULI

It is ironic that, considering their prominent form and frequency in the landscape, and their utility as sources of timber, paperbark and essential oils, the tropical and subtropical tree species of Melaleuca, collectively known either as the M. leucadendra group or the broad-leaved paperbarks, have proved so difficult for botanists to classify. Numerous species and varieties have been proposed but presently it is considered that there are 15 species in the group, the majority being medium to large trees although a few are shrubs or small, poorly formed trees. The distributions of the species are shown in Figures 2-5.

An indication of the lack of appreciation of the taxonomic limits in the broad-leaved paperbarks can be found in the number of type specimens applicable to this group of plants. To date, there are 45 type specimens but only 15 accepted species, whereas in the M. linariifolia group there are 6 types and 5 species. Bentham (1867) dealt with the confusing array of names and specimens known to him by recognising only a single species in his Flora Australiensis account of the genus, i.e. M. leucadendron. [The majority of authors have used Linnaeus' later spelling "leucadendron"; it was only in 1966 that the original spelling "leucadendra" was re-established in the edition of the International Code of Botanical Nomenclature published in that year (Lanjouw et al. 1966).] Bentham was followed by most botanists, although some, notably Cheel (1917), endeavoured to partition the variation into varieties.

Blake (1968) published an extremely detailed revision of the M. leucadendra group, based upon his extensive field knowledge and an excellent appreciation of the discriminatory value of indumentum (hair type) and floral morphology in development of a workable taxonomy for this group of plants. The work by Blake has provided a sound basis for subsequent research. Byrnes (1984, 1985, 1986) generally followed Blake's treatment of the paperbarks although he combined M. quinquenervia and M. viridiflora on the basis that the two species overlapped in the quantitative key characters given by Blake (1968). Byrnes (1984) described several new taxa in the group, notably a number at varietal level; presumably in part this was an acknowledgment of the regional differentiation within some of the species that had been more broadly defined by Blake. In the 1980's, B.A.Barlow and co-workers reworked the taxonomy of the group but, although several new taxa were recognised by them (and a number of Byrnes' were not), their results unfortunately have not been published in a synthetic account.

The species from which cajuput oil is extracted, M. cajuputi (Plate 4, 18, 19) is widespread and occurs from southeast Asia to northern Australia. However, the source of commercial cajuput oil are populations apparently originating in a restricted part of Indonesia and now cultivated more widely in both Indonesia and other parts of southeast Asia. These populations belong to a distinct form of the species, M. cajuputi subsp. cajuputi.

Figure 2 Distributions of Melaleuca species. 1, M. arcana. 2, M. argentea. 3, M. clarksonii. 4, M. cornucopiae

Figure 2 Distributions of Melaleuca species. 1, M. arcana. 2, M. argentea. 3, M. clarksonii. 4, M. cornucopiae

It is tempting to consider that the wide distribution of the species is a direct result of the fact that the species is of value for its therapeutic oil with man having carried the plant around to cultivate it. Once established in cultivation locally, it could then become naturalised and expand its range using natural means of dispersal. Barlow (1988) discussed patterns of differentiation in species of the M. leucadendra group, especially their geographic distributions. Barlow has recognised three subspecies within M. cajuputi: subsp. cajuputi, subsp. cumingiana and subsp. platyphylla. He considered that the western subspecies of M. cajuputi, subsp. cumingiana, represented a colonisation event across Wallace's Line from the east, an unusual event as most of the plant movements across this line have been from the west. This subject was taken up by Lum (1994). Lum concluded that genetic data supported the hypothesis that M. cajuputi had dispersed naturally westward. However, Lum's genetic data were derived from relatively few populations that do not sample the species across its range adequately; further work is required before an unequivocal assessment can be made.

Figure 3 Distributions of Melaleuca species. 5, M. cajuputi subsp. cajuputi. 6, M. cajuputi subsp. cumingiana. 7, M. cajuputi subsp. platyphylla

Figure 3 Distributions of Melaleuca species. 5, M. cajuputi subsp. cajuputi. 6, M. cajuputi subsp. cumingiana. 7, M. cajuputi subsp. platyphylla

The other species of the M. leucadendra group used as a source of essential oil is M. quinquenervia (Plate 5, 21-23), called niaouli in New Caledonia and the source of niaouli oil. This species occurs naturally in eastern Australia, southern New Guinea (including the southeast Papuan islands) and New Caledonia. It is cultivated for essential oil production in Madagascar (Ramanoelina et al. 1992, 1994) and is naturalised in the southeastern United States. Although M. quinquenervia could have arrived in New Caledonia from the southeast Papuan islands, it is more likely that it dispersed there from eastern Australia. As with M. cajuputi, very little is known about the degree of intraspecific variation. Molecular studies aimed at identifying markers that can be used to circumscribe provenance are required. Such studies may then enable light to be shed upon the origins of the New Caledonian population.

As far as future work on the M. leucadendra group is concerned, studies directed towards finding additional macrocharacters for distinguishing M. cajuputi from M. quinquenervia and M. viridiflora from M. quinquenervia need to be undertaken. Further investigations into essential oils are likely to be of interest; M. viridiflora, for example, has commercial potential as a source of methyl cinnamate from the oil (Chapter 16, this volume). Blake (1968) noted some examples of hybridisation between species in the M. leucadendra group and this needs further consideration. For example, is the difficulty in distinguishing M. cajuputi from M. quinquenervia due to hybridisation, and is the occasional occurrence of paper bark in the usually hard barked M. clarksonii due to hybridisation or is it part of the intrinsic variation of the species? Molecular techniques are likely to provide additional powerful tools in studying such questions.

List of species of the M. leucadendra group, including their synonyms and type specimens

1. Melaleuca arcana S.T.Blake, Contr. Queensland Herb. 1:54, figs. 10, 15J. (1968). Typus: Queensland: NW of Cooktown and W of Cape Bedford, Blake 20260 (BRI, holo, n.v.).

Melaleuca leucadendron var. albida f. ruscifolia Cheel, in Ewart & Davies, Fl. N. Territory 302 (1917). Melaleuca ruscifolia Sol. ex Cheel, in Ewart & Davies, Fl. N. Territory 302 (1917), nom. inval. Typus: Queensland: Point Lookout, Banks & Solander s.n. (NSW, holo, n.v.; BM, E, K, MEL, P, W, n.v., CANB, iso,).

2. Melaleuca argentea W.Fitzg., J. Proc. Roy. Soc. Western Australia 3:187 (1918). Typus: Western Australia: base of Mt. Bartlett, Sep. 1905, Fitzgerald 1258 (NSW, holo, n.v.; K n.v., PERTH, iso).

3. Melaleuca cajuputi Powell.

3a. Melaleuca cajuputi Powell subsp. cajuputi, Pharm. Roy. Coll. Physic. London (Transl.) 1809, 22 (1809). Myrtus saligna J.F.Gmel, Syst. nat. 793 (1791), nom. illeg., non Burm.f. Melaleuca trinervis Buch.-Ham., Mem. Wern. Nat. Hist. Soc. 6:302 (1832), nom. illeg., non Sm. in White. Melaleuca saligna (J.F.Gmel.) Blume, Mus. Bot. 1:66 (1849), nom. illeg., non Schauer. Melaleuca leucadendron var. cajuputi (Powell) Nied., Natürl. Pfl.Fam IV, 3. 7:95 (1893). Typus: Rumphius, Herb. Amboin. 2:76, t. 17, figs. 1, 2 (1741) (the figures and description).

Melaleuca minor Sm., in Rees, Cycl. 23, no. 2 (1812). Melaleuca leucadendron var. minor (Sm.) Duthie, in Hooker, Fl. Brit. India 2:465 (1878). Typus: Indonesia: Ceram, Amboina, Oct. 1796, Cbr. Smith 303 (LINN, holo, n.v.; BM, G, NSW, iso, n.v.).

Figure 4 Distributions of Melaleuca species. 8, M. dealbata. 9, M. fluviatilis. 10, M. lasiandra. 11, M. leucadendra. 12, M. nervosa subsp. crosslandiana. 13, M. nervosa subsp. nervosa

Figure 5 Distributions of Melaleuca species. 14, M. quinquenervia, 15, M. saligna, 16, M. sericea. 17, M. stenostachya. 18, M. viridiflora

Figure 5 Distributions of Melaleuca species. 14, M. quinquenervia, 15, M. saligna, 16, M. sericea. 17, M. stenostachya. 18, M. viridiflora

Melaleuca viridiflora var. angustifolia Blume, Bijdr. fl. Ned. Ind. 1099 (1826). Melaleuca angustifolia (Blume) Blume, Mus. Bot. 1:83 (1849), nom. illeg., non Gaertn. Typus: Indonesia: Moluccas, Amboina, herb. Blume s.n. (L, holo, n.v.; BRI, fragm., n.v).

Melaleuca lancifolia Turcz., Bull. Soc. Imp. Naturalistes Moscou 20:164 (1847). Melaleuca leucadendron var. lancifolia (Turcz.) F.M.Bailey, Syn. Queensl. f1. 170 (1883). Typus: Indonesia: Sumatera, Cuming2427 (KW, holo, n.v.; CGE, FI, K, P, W, iso, n.v). 3b. Melaleuca cajuputi subsp. cumingiana (Turcz.) Barlow, in Craven & Barlow, Novon 7:113 (1997). Melaleuca cumingiana Turcz., Bull. Soc. Imp. Naturalistes Moscou 20:164 (1847). Typus: Malaysia: Malaya, Malacca, Cuming 2272 (KW, holo, n.v.; BRI, CGE, FI, K, L, LE, MEL, MO, P, W, iso, n.v).

Melaleuca commutata Miq., Anal. bot. ind. 14 (1850). Typus: Borneo, Korthals s.n. (L, holo, n.v.; K, iso, n.v.). 3c. Melaleuca cajuputi subsp. platyphylla Barlow, in Craven & Barlow, Novon 7:113 (1997). Typus: Papua New Guinea: Western Province: near Bula village, mouth of Morehead River, 4 Aug. 1967, Pullen 6998 (CANB, holo; A, AD, BISH, BO, BRI, E, G, K, L, LAE, NSW, P, PNH, SING, TNS, US, iso, n.v). Notes

Myrtus saligna Burm.f. (Fl. Ind. 116 (1768)) was included in the synonymy of M.cajuputi by Blake (1968) but its type (Indonesia: Java, 1760, leg. ign. s.n. (G, holo, n.v.)) needs to be examined before the name can be assigned to one of the above subspecies.

Melaleuca eriorhachis Gand. (Bull. Soc. Bot. France 65:26 (1918)) also was referred to M.cajuputi by Blake (1968). Its type (Singapore, Ridley (?) s.n. (LY, holo, n.v.)) similarly needs to be studied before confident placement to subspecies is possible.

4. Melaleuca clarksonii Barlow, in Craven & Barlow, Novon 7:114 (1997). Typus: Queensland: Cape York Peninsula, 11.1km SSE of Emu Lagoon, Alice River National Park, 7 May 1992, Clarkson andNeldner 9582 (CANB, holo; BRI, DNA, K, L, MBA, MEL, NSW, PERTH, iso).

5. Melaleuca cornucopiae Byrnes, Austrobaileya 2:74 (1984). Typus: Northern Territory: Koongarra, 16 Nov. 1975, Dunlop 4030 (BRI, holo, n.v.; DNA, iso, n.v.).

6. Melaleuca dealbata S.T.Blake, Contr. Queensland Herb. 1:41, figs. 5, 14E, 15E, 15N. (1968). Typus: Northern Territory: c. Lat. 12 40 S, Long. 131 25 E, Blake 17000 (BRI, holo, n.v.; CANB, iso).

7. Melaleuca fluviatilis Barlow, in Craven & Barlow, Novon 7:116 (1997). Typus: Queensland: sandy river bed, Bruce Highway, c. 50km NW of Townsville, 13 Jul. 1985, Barlow and Thiele 3940 (CANB, holo).

Melaleuca nervosa f. pendulina Byrnes, Austrobaileya 2:74 (1984). Typus: Queensland: Coen River, Brass 19778 (BRI, holo, n.v.; A, n.v., CANB, iso).

8. Melaleuca lasiandra F.Muell., Fragm. 3:115 (1862). Myrtoleucodendron lasiandrum (F.Muell.) Kuntze, Revis. gen. pl. 241 (1891). Syntypi: Northern Territory: Fitzmaurice River, Oct. 1855, Mueller s.n.; Victoria River, Jan.—May 1856, Mueller s.n. (both MEL, n.v.).

Melaleuca loguei W.Fitzg., J.Proc. Roy. Soc. Western Australia 3:188 (1918). Typus: Western Australia: S of the Fitzroy River, Logue in Fitzgerald s.n. (NSW, holo, n.v.).

9. Melaleuca leucadendra (L.) L., Mant. pl. 1:105 (1767). Myrtus leucadendra L., Sp. pl. ed. 2, 676 (1762). Leptospermum kucadendron (L.) J.R. & G.Forst., Char. gen. pl. 72 (1776). Cajuputi leucadendron (L.) Rusby ex A.Lyons, Pl. names Sci. Pop. 479 (1900). Lectotypus (fide Blake, Contr. Queensland Herb. 1:17 (1968)): Rumphius, Herb. Amboin. 2:72, t. 16 (1741) (the figure and description).

Melaleuca mimosoides Schauer, in Walpers, Repert. Bot. Syst. 2:927 (1843). Melaleuca leucadendron var. mimosoides (Schauer) Cheel, in Ewart & Davies, Fl. N. Territory 295 (1917). Typus: Queensland: Rockingham Bay and Endeavour River, Cunningham 253/1819 (BM, K, iso, n.v.).

Melaleuca amboinensis Gand., Bull. Soc. Bot. France 65:26 (1918). Typus: Indonesia: Ceram, Amboina, de Vriese s.n. (LY, holo, n.v.).

10. Melaleuca nervosa (Lindl.) Cheel.

10a. Melaleuca nervosa (Lindl.) Cheel subsp. nervosa, J. Proc. Roy. Soc. New S.Wales 78:65 (1944). Callistemon nervosus Lindl., in Mitchell, J. exped trop. Australia 235 (1848), as nervosum. Melaleuca leucadendron var.? parvifolia Benth., Fl. Austral. 3:143 (1867), pro parte (as to C.nervosus). Melaleuca leucadendron var. nervosa (Lindl.) Domin, Biblioth. Bot. 89:457 (1928), nom. illeg. Typus: Queensland: Balmy Creek, Jul. 1846, Mitchell 241 (CGE, holo, n.v.; MEL, NSW, iso, n.v.).

Melaleuca nervosa f. latifolia Byrnes, Austrobaileya 2 (14 Jul. 1984) 74. Typus: Northern Territory: about SE of Brooks Creek, Jul. 1946, Blake 16344 (BRI, holo, n.v).

10b. Melaleuca nervosa subsp. crosslandiana (W.Fitzg.) Barlow ex Craven, comb, et stat. nov. Melaleuca crosslandiana W.Fitzg., Western Mail (Perth) (2 Jun. 1906), basionym. Melaleuca leucadendron var. coriacea f. crosslandiana (W.Fitzg.) Cheel, in Ewart & Davies, Fl. Northern Territory 298 (1917). Lectotypus (fide Blake, Contr. Queensland Herb. 1:43 (1968)): Western Australia: base of Mt Harris, Jun. 1905, Fitzgerald 1116 (BRI n.v., NSW).

11. Melaleuca quinquenervia (Cav.) S.T.Blake, Proc. Roy. Soc. Queensland 69:76 (1958). Metrosideros quinquenervia Cav., Icon. 4:19, t. 333 (1797). Typus: New South Wales: Port Jackson, Apr. 1793, Née s.n. (MA, n.v., specimen now lost but the illustration forming part of the protologue is available).

Metrosideros coriacea Poir., Encycl. Suppl. 3:685 (1813), nom. illeg., non Salisb. Melaleuca leucadendron var. coriacea (Poir.) Cheel, in Ewart & Davies, Fl. N.Territory 297 (1917). Typus: New Caledonia: Labillardiére s.n. (FI, holo, n.v.; MEL, P, n.v.).

Melaleuca leucadendron ß angustifolia L.f., Suppl. pl. 342 (1781). Melaleuca viridiflora var. angustifolia (L.f.) Byrnes, Austrobaileya 2:74 (1984), nom. illeg., non Bl. Typus: New Caledonia: Forster s.n. (LINN, holo, n.v.; K, iso, n.v.). Melaleuca viridiflora var. ß rubriflora Brongn. & Gris, Bull. Soc. Bot. France 11:183 (1864). Melaleuca rubriflora Vieill. ex Brongn. & Gris, Bull. Soc. Bot. France 11:183 (1864), nom. inval. Melaleuca leucadendron var. rubriflora (Brongn. & Gris) Guill., Ann. Inst. Bot-Geol. Colon. Marseille 19:73 (1911). Typus: New Caledonia: near Balade, Vieillard 451 (P, holo, n.v.).

Melaleuca maideni R.T.Baker, Proc. Linn. Soc. New South Wales 38:598 (1914). Lectotypus (fide Blake, Contr. Queensland Herb. 1:28 (1968)): New South Wales: Port Macquarie, Jul. 1895, Maiden s.n. (NSW, lecto, n.v.).

Melaleuca smithii R.T.Baker, Proc. Linn. Soc. New South Wales 38:599 (1914). Lectotypus (fide Blake, Contr. Queensland Herb. 1:28 (1968)): New South Wales: Rose Bay, Jul. 1913, Laseron s.n. (NSW, lecto, n.v.).

Melaleuca leucadendron var. albida Cheel, in Ewart & Davies, Fl. Northern Territory 301 (1917), excl. forma ruscifolia Cheel. Lectotypus (fide Blake, Contr. Queensland Herb. 1:28 (1968)): New South Wales: SieberFl. Nov. Holl. 319 (MEL, M, K, isolecto, n.v.).

Melaleuca leucadendron var. vel forma nana Brongn. & Gris ex Guill., Bull. Soc. Bot. France 81:6 (1934). Typus: New Caledonia: near Nouméa, Balansa 99 (P, holo, n.v.).

Melaleuca leucadendron var. vel forma latifolia Guill., Bull. Soc. Bot. France 81:6 (1934), nom. illeg., non L.f. Typus: New Caledonia: near Nouméa, Balansa 99 (P, holo, n.v.).

12. Melaleuca saligna Schauer, in Walpers, Repert. Bot. Syst. 2:927 (1843). Melaleuca leucadendron var. saligna (Schauer) F.M.Bailey, Syn. Queensl. fl. 170 (1883). Typus: Queensland: swampy banks of the Endeavour River, Cunningham 256/1819 (BM, iso, n.v.).

Melaleuca stenostachya var. pendula Byrnes, Austrobaileya 2:74 (1984). Typus: Queensland: Jacky Jacky airstrip, Bamaga district, May 1962, Webb & Tracey 5989 (BRI, holo, n.v.; CANB, QRS n.v.).

13. Melaleuca sericea Byrnes, Austrobaileya 2:74 (1984). Typus: Western Australia: 15km W of Tableland Station, Apr. 1955, Lazarides 5133 (BRI, holo, n.v.; CANB, iso).

14. Melaleuca stenostachya S.T.Blake, Contr. Queensland Herb. 1:50, figs. 8, 14 H, 15 H (1968). Typus: Queensland: Croydon, Blake 19566 (BRI, holo, n.v.).

15. Melaleuca viridiflora Sol. ex Gaertn., Fruct. sem. plantarum 1 (Dec. 1788) 173, t. 35, fig. 1. Myrtoleucodendron viridiflorum (Sol. ex Gaertn.) Kuntze, Revis. gen. pl. 1:241 (1891). Cajuputi viridiflora (Gaertn.) A.Lyons, Pl. names Sci. Pop. 74 (1900). Melaleuca leucodendron var. viridiflora (Gaertn.) Cheel, in Ewart & Davies, Fl. Northern Territory 299 (1917). Typus: Queensland: Endeavour River, Jul.—Aug. 1770, Banks and Solander s.n. (BM, MEL, NSW, iso, n.v.).

Melaleuca cunninghami Schauer, in Walpers, Repert. Bot. Syst. 2:927 (1843). Melaleuca leucadendron var. cunninghamii (Schauer) F.M.Bailey, Syn. Queensl. fl. 171 (1883). Typus: Queensland: Endeavour River, Cunningham s.n. (K, iso, n.v.).

Melaleuca leucadendron var. latifolia Rivière, Bull. Soc. Nat. Acclim. France III, 9:537 fig. 1 (1882). Syntypi: Northern Territory: Gulf of Carpentaria, Mueller s.n. (P, K, n.v.; MEL isosyn, n.v.), nom. illeg., non L.f.

Melaleuca leucadendron var. sanguinea (Sol. ex Cheel) Cheel, in Ewart & Davies, Fl. N. Territory 296 (1917), nom. illeg. Melaleuca sanguinea Sol. ex Cheel, Fl. N. Territory 296 (1917), nom. inval. Typus: Queensland: Endeavour River, Jul.—Aug. 1770, Banks & Solander s.n. (NSW, holo, n.v.; BM, MEL, P, W, iso, n.v.).

Melaleuca cunninghamii var. glabra C.T.White, J.Arnold Arbor. 23:87 (1942). Melaleuca viridiflora var. glabra (C.T.White) Byrnes, Austrobaileya 2:74 (1986). Typus: Papua New Guinea: Tarara, Brass 8485 (BRI, holo, n.v.; A, K, LAE, n.v.).

Melaleuca viridiflora var. attenuata Byrnes, Austrobaileya 2:74 (1984). Typus: Queensland: outside Port Douglas, c. 11km ESE of Mossman, Jul. 1967, Moriarty 9 (BRI, holo, n.v.).

Melaleuca viridiflora var. canescens Byrnes, Austrobaileya 2:74 (1984). Typus: Queensland: 48km SSE of Strathleven homestead, Nov. 1965, Pedley 1843 (BRI, holo, n.v.).

Key to the species of the M. leucadendra group

Note: Young growth may be needed to observe the leaf hairs as these are soon deciduous in some species.

1. Calyx lobes absent M. cornucopiae

1. Calyx lobes present

2. Staminal filaments hairy M. lasiandra

2. Staminal filaments glabrous 3. Hypanthium distinctly hairy

4. Leaf blade indumentum with at least some of the hairs lanuginulose or sericeous-lanuginulose (whether or not also with pubescent to sericeous or sericeous-pubescent hairs) 5. Stamens 5-8mm long

6. Calyx lobes 0.5-0.8mm long; triads clustered (less than 1 hypanthium diameterapart) M. saligna

6. Calyx lobes 0.9-1.5mm long; triads scattered (more than 1 hypanthium diameter apart) or sometimes partly clustered M. dealbata

5. Stamens 10-23mm long

7. Leaves 1.6-10.2 times as long as wide, the blade 5-40mm wide; hypanthium 1.8-3.5mm long; stamens 3-7 per bundle

8. Leaf blade tardily glabrescent; leaves 9-40 mm wide, 1.6-8.8 times as long as wide M. nervosa subsp. nervosa

8. Leaf blade soon glabrescent; leaves 5-30 mm wide, 2.8-10.2 times as long as wide M. nervosa subsp. crosslandiana

7. Leaves 5-20 times as long as wide, the blade 5-19mm wide; hypanthium

I.3-2mm long; stamens 3-9 per bundle M. fluviatilis

4. Leaf blade indumentum without lanuginulose or sericeous-lanuginulose hairs (the hairs sericeous, sericeous-pubescent or pubescent) 9. Inflorescence up to 30mm wide 10. Inflorescence up to 20mm wide

II. Triads distant (at least 1 hypanthium diameter apart, sometimes within an inflorescence some of the triads are closer)

M. stenostachya

11. Triads clustered (less than 1 hypanthium diameter apart)

12. Leaf blade apex acuminate, narrowly acute or acute M. sericea

12. Leaf blade apex usually obtuse, sometimes acute, rounded, obtusely shortly acuminate or refuse M. arcana

10. Inflorescence more than 20mm wide

13. Calyx lobes herbaceous in the proximal-central zone and scarious in a narrow marginal band; leaves 4.8-14 times as long as wide M. argentea

13. Calyx lobes herbaceous in the proximal-central zone and scarious in a broad marginal band; leaves 1.3-9.7 times as long as wide

14. Older leaves with the secondary venation distinct and about as prominent as the major veins 15. Leaves (17-)25-50(-60) mm wide (leaves 1.3-6.5 times as long as wide; stamens (8-)9-12(-15) per bundle)

M. cajuputi subsp. platyphylla

16. Leaves (6-)10-16(-26)mm wide, 2.8-9.7 times as long as wide; stamens (6-)8-11(-14) per bundle

M. cajuputi subsp. cajuputi

16. Leaves (15-)19-28(-39)mm wide, 2.2-2.9 times as long as wide; stamens (4-)6-8(-10) per bundle

M. cajuputi subsp. cumingiana

14. Older leaves with the secondary venation more or less obscure M. quinquenervia

9. Inflorescence more than 30mm wide

17. Young shoots with the hairs completely appressed; hypanthium (1.8-)3-3.5mm long; petals (2.7-)4-5.3mm long; inflorescence axis sericeous or pubescent (occasionally glabrous) M. viridiflora

17. Young shoots with at least some spreading-ascending to spreading hairs; hypanthium 1.5-2.5 mm long; petals 2.5-3.5 mm long; inflorescence axis pubescent M. quinquenervia

3. Hypanthium glabrous or effectively so

18. Calyx lobes puberulous on the abaxial surface M. dealbata

18. Calyx lobes glabrous on the abaxial surface

19. Calyx lobes herbaceous in the proximal-central zone and scarious in a narrow marginal band or the lobes herbaceous almost throughout

20. Stamens 6-7mm long; leaves 30-110mm long, 3.3-9 times as long as wide; bark hard M. clarksonii

20. Stamens 7-16mm long; leaves 75-270mm long, 3.5-16.1 times as long as wide; bark papery M. leucadendra

19. Calyx lobes herbaceous in the proximal-central zone and scarious in a broad marginal band

21. Leaf blade narrowly ovate, very narrowly ovate, rarely narrowly elliptic or very narrowly elliptic (often falcate to subfalcate); leaves 3.5-16 times as long as wide; petals with elliptic oil glands (occasionally long elliptic glands form an apparently linear gland) M. leucadendra

21. Leaf blade elliptic to very narrowly elliptic, obovate to very narrowly obovate (rarely broadly elliptic or ovate or very narrowly ovate or approaching falcate); leaves usually 1.3-8.5 times as long as wide (in some forms of M. viridiflora 4.8-15.7 times as long as wide with the blade very narrowly elliptic or narrowly elliptic or narrowly obovate or very narrowly obovate); petals with oil glands linear, elliptic, circular to subcircular, or oblong

22. Stamens 9.2-10mm long, the bundle claw 0.2-0.4

times as long as the stamens

M. cajuputi subsp. platyphylla

22. Stamens (9.5-)10.5-23mm long, the bundle claw 0.06-0.2(-0.5) times as long as the stamens 23. Hypanthium 1.5-2.5mm long; petals 2.53.5mm long; leaves 10-30mm wide;

inflorescence axis pubescent

M. quinquenervia 23. Hypanthium (1.8-)3-3.5mm long; petals (2.7-)4-5.3mm long; leaves (8-)19-76mm wide; inflorescence axis sericeous or pubescent

(occasionally glabrous) M.

viridiflora

ACKNOWLEDGMENTS

The assistance of Brendan Lepschi in collecting data and references, and of Julie Matarczyk in producing the distribution maps, is much appreciated. Bryan Barlow's specimen annotations and notes concerning type specimens were valuable in treating the M. leucadendra group.

REFERENCES

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Barlow, B.A. (1988) Patterns of differentiation in tropical species of Melaleuca L. (Myrtaceae). Proc.

Ecol. Soc. Australia, 15, 239-247. Barlow, B.A. and Cowley, K.J. (1988) Contributions to a revision of Melaleuca (Myrtaceae): 4-6.

Austral. Syst. Bot., 1, 95-126. Bentham, G. (1867, '1866') Myrtaceae. In, FloraAustraliensis, Vol. 3, Lovell Reeve & Co., London, pp. 1-289.

Blake, S.T. (1958) New and critical genera and species of Myrtaceae subfamily Leptospermoideae from eastern Australia. Proc. Roy. Soc. Queensland, 69, 75-88. Blake, S.T. (1968) A revision of Melaleuca leucadendron and its allies (Myrtaceae) Contr. Queensland Herb., 1, 1-114.

Briggs, B.G. and Johnson, L.A.S. (1979) Evolution in the Myrtaceae—evidence from inflorescence structure. Proc. Linn. Soc. New South Wales, 102, 157-256. Butcher, P.A., Doran, J.C. and Slee, M.U. (1994) Intraspecific variation in leaf oils of Melaleuca alternifolia (Myrtaceae). Biochem. Syst. Ecol., 22, 419-430. Butcher, P.A., Byrne, M. and Moran, G.F. (1995) Variation within and among the chloroplast genomes of Melaleuca alternifolia and M. linariifolia (Myrtaceae). Pl. Syst. Evol., 194, 69-81. Byrnes, N.B. (1984) A revision of Melaleuca L. (Myrtaceae) in northern and eastern Australia, 1. Austrobaileya, 2, 65-76.

Byrnes, N.B. (1985) A revision of Melaleuca L. (Myrtaceae) in northern and eastern Australia, 2. Austrobaileya, 2, 131-146.

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Lanjouw, J., Mamay, S.H., McVaugh, R., Robyns, W., Rollins. R.C., Ross, R., Rousseau, J., Schulze, G.M., Vilmorin, R. de and Stafleu, F.A. (1966) International code of botanical nomenclature, International Bureau for Plant Taxonomy and Nomenclature, Utrecht.

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