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Subser. Plurinerves

Sect. Heterophyllum

Sect. Plurinerves

Sect. Plurinervia

Subser. Juliflorae Subsect. Spiciferae Subser. Brunioideae

Ser. Pulchellae Sect. Pulchelloidea

Sect. Juliflorae

Sect. Lycopodiifoliae Sect. Lycopodiifoliae Sect. Pulchellae Sect. Pulchellae

Subser. Juliflorae Subsect. Spiciferae Subser. Brunioideae

Ser. Pulchellae Sect. Pulchelloidea

Sect. Juliflorae

Sect. Lycopodiifoliae Sect. Lycopodiifoliae Sect. Pulchellae Sect. Pulchellae

*Nomenclature likely to be adopted following the success of the proposal by Orchard and Maslin (2003).

flower heads. In some species, however, the distinction between the two states is blurred, i.e. some species have obloid heads and both head shapes may be represented in otherwise allied taxa. Simple and racemose inflorescences are represented in both groups and, as with the Phyllodineae and Botrycephalae, intersectional hybrids between the two groups are known. As noted by Maslin et al. (2003), further study of these large sections is required before a more meaningful infrageneric classification can be elucidated.

Species from the endemic sections Alatae (c. 20 spp. from south-western Western Australia), Lycopodiifoliae (c. 17 mainly tropical spp.) and Pulchellae (c. 27 spp. from south-western Western Australia) comprise mainly low shrubs. Subgenus Acacia/gen. Vachiella has over 150 species represented in the New World, Africa and Asia with about seven species endemic to tropical Australia. There are two species (one endemic) from subgen. Aculeiferum/gen. Senegalia in Australia, both occuring as woody vines in the rainforests of far north-eastern Queensland. None of these latter groups are represented by species treatments presented here; for more information the reader is referred to Maslin (2001a) and Maslin et al. (2003).

Identification

A principal character used in most keys for the identification of species is the foliage. The nervation of the phyllodes is of considerable importance, i.e. one-nerved versus numerous nerves while both in the phyllodinous and bipinnate species glands (extra-floral nectaries) are useful but indumentum less so. Stipules are useful but they may be minute or early deciduous. The type of inflorescence, i.e. simple versus racemose, is of major importance, while the approximate number of flowers in a head can be of value in identification. When available the pods are helpful in separating species—whether pods are straight, twisted or coiled; whether parallel-sided or moniliform and whether the seed is aligned transversely or longitudinally in the legume. The seeds and their appendages are sometimes of great value in separating two species, which may have a superficial resemblance in the field, e.g. a difference in arils will readily separate A. implexa from A. melanoxylon (the aril completely surrounds the seed in A. melanoxylon). Accurate identification of wattles has recently been greatly facilitated with the advent of electronic interactive identification. Maslin (2001) is a LUCID-based electronic key that enables the user to readily identify 1165 wattles from throughout Australia.

Biology

There is a marked difference in the longevity of species and, while detailed records are not available, certain generalisations are possible. Acacia baileyana, a shrub of the sub-humid area, when planted on dry and otherwise unfavourable sites may commence to deteriorate at 10-12 years. Many of the large shrub/small tree bipinnate species of the coastal area may grow very fast in early life, e.g. average 2 m a year for 5 years, and have a life span of 25-50 years. Medium to large shrubs of the dry country, however, appear to have longer lives and in the case of A. catenulata one small tree has been recorded as over 50 years of age and still vigorous. Of undoubted longevity is A. melanoxylon, which probably exceeds 100 years, and waddy (A. peuce), dated at 500 years old.

The seed of most acacias has an almost impervious testa and may remain viable up to at least 20 years. Pretreatment before sowing is necessary to break the dormancy; the simplest way for many species is to place the seed in water which has just boiled and allow it to cool. One striking exception is the seed of A. harpophylla which, if not stored at freezing or subfreezing temperatures, may only remain viable for 0.5-2 years. The average number of seeds per kilogram for most acacia species is in the range 40 000-60 000.

Overseas experience, especially in areas of moderate rainfall—say 750-1250 mm—is that acacias introduced from Australia may become a weed and displace native vegetation. Two possible explanations are that fire may destroy native fire-sensitive shrubs while inducing germination of acacia seed, or that the introduced acacias are less critical in their nutrient requirements. In addition, the introduced species often have a faster early growth rate and are free from natural pests and predators in their new environment.

Uses

Associated with their widespread natural occurrence, acacias also play an important role in soil conservation, as a source of nitrogen in forest ecosystems and as fodder plants. Not only are they of use as drought fodder but in the drier parts of the continent they have an important role as browse plants. Some authorities consider that A. aneura is the most important fodder tree in Australia because it is widespread, abundant and usually palatable although not notably nutritious. It is mainly a fodder for sheep. With this, as with some other species, there is considerable geographic variability in palatability and local observations are needed before lopping is done in time of drought. Most acacias cause impaction in stock if eaten as the sole diet and are better when taken as a supplement to other food. Among other phyllodinous species eaten are A. coriacea, A. excelsa and A. pendula, while less favoured are A. brachystachya, A. cana and A. georginae. Only a few bipinnate species are eaten by stock, such as A. deanei and A. farnesiana, with the latter having its main natural occurrence overseas. In Europe some species are grown for the flowers and sold under the name of 'mimosa'. The flowers, however, while producing a moderate amount of pollen are generally of limited value as a source of nectar for honey production. Acacias are useful for shade, shelter and ornamental planting, though care has to be taken in the selection of species and their probable longevity.

Wattleseed as a source of human food has been a subject of increasing interest and research in recent years. Much of this work is based on an understanding of traditional Aboriginal use. Harwood (1994) documented species such as A. elachantha (kalkardi), A. thomsonii

(Thomson's wattle), A. tumida (Pindan wattle) and particularly A. colei (Cole's wattle), as showing promise as a new source of human food in semi-arid regions of the Sahel, West Africa. The seeds are readily processed using local technology and the ground flour has been incorporated into local recipes. These species were originally introduced into Africa for fuelwood and windbreaks and they are still used in these roles. In Australia, wattleseed is used in the bushfood industry and ground roasted seeds are mainly used for flavouring sauces and ice cream, and in breads, pasta and biscuits. Most of this seed is currently collected from natural populations of gundabluey (A. victoriae) but other species, including A. colei are also important. Maslin et al. (1998) identified 47 species as having potential for edible seed production in southern Australia.

The bark of most acacias has significant tannin content which, in some species, may be as high as 45 per cent. One of the most notable in this respect is A. mearnsii, which is cultivated extensively in South Africa, and A. pycnantha from which bark was formerly collected in southern Australia. The sapwood of most species is very narrow—usually less than 2 cm—while the heartwood is typically dark in colour (dark brown to almost black, dark golden brown or yellow, sometimes streaked with dark yellow or red), heavy, hard, sometimes finely figured, strong, tough and usually durable in the ground. It can be worked to a fine finish and takes a high polish. Several species were highly favoured by Aboriginal people for weapons, including spears and clubs, and for making boomerangs. In the earlier days of European settlement the wood was highly favoured for cabinet making and furniture, but because of its heaviness, is now less favoured than formerly. A modern use of A. melanoxylon is in sliced veneer on a lightweight base such as particleboard. Some woods have a distinctive scent, e.g. jam (A. acuminata), which has the fragrance of raspberry jam and myall (A. pendula), which has a violet-like fragrance. Further information on the uses of wattles is given in Doran and Turnbull (1997), McDonald et al. (2001) and Maslin and McDonald (2004).

Acacias are represented in most parts of Australia, ranging from tall forest trees to low sprawling shrubs. Some are cultivated overseas for their hardiness and rapid growth. 1. Gidgee (Acacia cambagei), Oodnadatta Track, S.A. 2. Granite wattle (A. quadrimarginea), near Laverton, W.A. 3. Cole's wattle (A. colei) cultivated in Maradi, Niger, for shade, firewood and human food. 4. Brigalow (A. harpophylla), near Adavale, Qld. 5. An exceptionally large ear-pod wattle (A. auriculiformis), Tiwi Islands, N.T.

Jam Raspberry Jam

Acacia acuminata Benth.

Jam commonly grows as a large, bushy shrub 3-5 m tall with a short main stem, which divides about 1 m from the ground into numerous fine spreading-erect branches. On very favourable sites in the western part of its occurrence it may be a small tree 10 m tall, with trunks 2-2.5 m in length. There are two subspecies, the typical and subsp. burkittii.

Subsp. acuminata occurs in south-western Western Australia where it is still common throughout the wheat belt, especially in an area 50-300 km inland from Perth and roughly parallel to the coast. It extends south from the Murchison River area to Borden and Ravensthorpe and east to Yalgoo, Kalgoorlie and Balladonia. Subsp. burkittii extends west from subsp. acuminata, through inland South Australia to the western plains of New South Wales.

Subsp. acuminata occurs mainly on gently undulating topography of the Yilgarn Plateau. The soils are often lateritic gravels, but range from pale brown clays and darker clays on flats to red sand and granitic gravels. Subsp. burkittii grows in low open woodlands and shrub-lands on plains or on dunes. Soils are often calcareous red or brown sandy loams or sands.

Jam attains its best development in woodlands where the main associated tree eucalypts are York gum (E. loxophleba) and salmon gum (E. salmonophloia). Associated shrubs include a wide range of acacias, especially A. microbotrya. Subsp. burkittii occurs in open shrublands often in dense pure stands or associated with numerous other acacias including mulga (A. aneura) communities and in the east poplar box (E. populnea), cypress pine (Callitrisglaucophylla) and mallee eucalypt communities.

Related species: Jam (sect. Juliflorae) comprises a number of variants, documented by Maslin and McDonald (2004) and is allied to Oldfield's wattle (A. oldfieldii). This species mainly differs in having adult phyllodes with glabrous margins, longer peduncles and spikes that are less densely flowered.

Publication: Subsp. acuminata: Hooker's London J. Bot. 1, 373 (1842). Type: includes collections by J. Drummond, Swan River, and W. Baxter, King Georges Sound, Western Australia. Subsp. burkittii Kodela & Tindale: Telopea 7, 415 (1998). Type: Lake Gilles in the interior, South Australia, W.C. Burkitt.

Names: Botanical—Latin acuminatus (pointed, elongated, or tapering), in allusion to the drawn-out tips of the phyllodes; burkittii honours W.C. Burkitt (1839-1908), a sheep farmer who collected the type. Common—an allusion to the odour of freshly cut timber.

Bark: On the lower half of the trunk of trees 0.3 m diameter it is up to 2 cm thick, hard, deeply furrowed longitudinally, grey to dark greyish. On smaller stems it may be lighter in colour, grading to a smooth thin greenish grey bark above.

Foliage: Cotyledons—sessile, elliptical up to 0.4 X 0.2 cm. Juvenile—alternate, first leaf pinnate (3-5 pairs of leaflets) with two narrow acuminate stipules at the base of the compound leaf, becoming bipinnate (4-5 pairs of pinnae)

early and then phyllodinous at about node 2 or 3; phyllodes long, narrow, falcate with fine longitudinal nerves, up to 15 X 0.8 cm. Adult—phyllodinous, alternate, linear and sometimes falcate, slightly coriaceous, 7.5-25 X 0.1-0.9 cm (acuminata), or linear-filiform, upright, terete to subterete and only 0.05-0.2 cm wide and apex delicately curved (burkittii), nerves numerous, fine and parallel to the midrib, with 1-3 veins more prominent than the others, (acuminata) or the central nerve often more prominent (burkittii); ciliolate particularly towards apices.

Inflorescences: Simple, axillary spikes, 1-2(-3) per axil, spikes 1-3.5 cm long (acuminata), or 0.5-1.5 cm long (burkittii), sessile or almost sessile, flowers densely arranged along rachis, bright yellow to golden; flowers mostly 4-merous, sepals partially fused. Flowers Jul.-Sept. (Oct.).

Fruits: Pods, linear, strongly raised over seeds, straight or slightly curved, (acuminata) or moniliform (burkittii), 5-15 X 0.3-0.7 cm, chartaceous, medium to dark brown. Seeds longitudinally aligned in pod, obloid to broadly ellipsoid or globoid, dark brown to brownish black, aril/funical cream. Mature Nov.-Jan.

Wood: Heartwood dark reddish brown, with distinctive odour when freshly cut reminiscent of raspberry jam, very hard, very durable in the ground, very dense, density about 1040 kg m-3; grain close and fine-textured, attractive appearance often with fiddleback; boles favoured for round fencing material; wood is also used for ornamental articles, machine bearings and sheave blocks.

Climate: Altitudinal range: near sea level to 400 (acuminata), 110-520 m (burkittii); Hottest/coldest months 32-34°C/4-7°C (acuminata), 33-38°C/3-7°C (burkittii); Frost incidence: low to moderate; Rainfall: 225-500 mm per year, winter (acuminata), 130-440 mm per year, uniform (burkittii).

Distinctive features: Phyllodes acuminate, with numerous fine longitudinal veins, finely ciliolate, particularly towards apices; spikes sessile or almost sessile; flowers mostly 4-merous; freshly cut wood is fragrant and reminiscent of raspberry jam.

Acacia acuminata: subsp. acuminata (a), subsp. burkittii (b) 1. Adult phyllodes (a) 2. Fruiting twig (a) 3. Seedling (a) 4. Flowering twig (a) 5. Flower buds 6. Shrub, near Wiluna, W.A. (b) 7. Tree, near Katanning, W.A. (a) 8. Bark

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