Eschweilera Long I

FIG 9. Medial sections of the androecia of selected species of New World Lecythidaceae. Note different degrees of zygomorphy, increase in starainal sterilization, and increasing complexity of the hood.

FIG 10. Photographs of selected species of New World Lecythidaceae which illustrate different structures of the androecium. A, Gustavia superba (unvouchered), note the actinomorphic an-droecium with many stamens; B, Grins neuberthii (Prance 16572), note the actinomorphic androecium with fewer stamens; C, Couroupita subsessilis (Prance et al 24382), note the zygomorphic androecium and the notch in the hood; D, Couroupita guianensis (Mori & Kallunki 2992), note the zygomorphic, open androecium and the anthers on the hood appendages; E, Lecythis alba (Mori & Bolten 8688), note the zygomorphic, open androecium and the anthers on the position which makes them more readily accessible to insects (Fig 10A). Zygomorphic-flowered species usually have the hood arranged in such a way that it serves as a landing platform for the pollinators (Fig IOC, F, G), In order to facilitate our discussion of flower orientation and insect visitation we have used the following terms (Fig 8):

Proximal—the bottom of the flower, i e the end attached to the pedicel; distal—the top of the flower, i e the end furthest removed from the pedicel; posterior—the ligular side of the flower;

anterior—the side of the flower opposite the ligule, i e the open side of the flower through which the pollinator usually enters;

lateral—the remaining two sides of the flower, these are often blocked to insect entry by the petals.

The hood of the androecium almost always serves as a landing platform for pollinators. Consequently, the anterior end either points upwards so that insects can land on the upper edge (Fig 10F), or the distal end of the flower faces the ground so that the entire inner surface of the hood acts as the landing platform (Fig 10D, E). In species with closed flowers, the hood also acts as a spring which forces the insect's back against the anthers of the staminal ring and, at the same time, against the stigma, which protrudes through the center of the staminal ring.

According to Miers (1874) and Knuth (1939b), the stamens of the Lecythidaceae arise at the tips of swollen structures called stamen appendages. These authors restrict the term filament to the minute constriction between the stamen appendage and the anther (Fig 8D). In his study of the staminal zygomorphy of Couroupita guianensis, Thompson (1921, p 3) considered each inner stamen (i e stamen of the staminal ring) to consist of "a short upright clavate and fleshy filament of pale yellow color (text-fig 2, and figs, 7 and 9). Distally it is continued into a short thread-like connective surmounted by a subglobose basifixed anther." Thompson, therefore disagrees with Miers and Knuth, calling the stamen appendage and filament of the other two investigators the filament and connective respectively. Thompson (1921, p 9) further adds that "there is no structural evidence in support of the view taken by Miers regarding these stamens, according to which the anther and the short connective—which has not yet arisen—are alone component parts of the stamen." We also agree with Thompson that the'small attenuation subtending the anther is part of the filament. It is a connective between the filament proper and the anther.

Evolution of the gynoecium has occurred in the position of the ovary in relation to the other floral parts, in the number of locules, and in the position of the placenta within the locule. The ovary may be completely inferior, i e truncate at the summit (e g all species of Gustavia, Grias, Bertholletia, and hood appendages; F, Lecythis corrúgala (Mori & Bollen 8682), note the zygomorphic, closed androecium; G, Eschweilera sp (Mori & Bollen 8637), note the zygomorphic, closed androecium; H, Couratari atrovinosa (Prance el al 23444), note the zygomorphic, closed androecium with the extra flap at the summit of the hood.

Lecythis) or it may be half-inferior, i e bulged upward at the summit (e g all species of Couroupita and many species of Eschweilera).

The number of locules per ovary is relatively constant in most genera and is a useful generic character. However, there is some intraspecific variation and therefore several flowers should be examined to determine the most frequent locule number. Eschweilera and Corythophora are characterized by 2-locular ovaries, Cariniana and Couratari by 3-locular ovaries, Grias, Allan-toma, Bertholletia, and Lecythis by 4-locular ovaries, and Couroupita by 6-locular ovaries. Ovaries of species of Gustavia have 4 or 6 locules and those of Asteranthos have 5 to 8 locules. Sapucaya and Pachylecythis have been segregated from Lecythis on the basis of locule number. However, we feel that the 6 locules of the former and the 5 locules of the latter are variants on the usual number of 4 in Lecythis and therefore these genera do not merit taxonomic recognition.

The ovules may be attached to a swollen placenta at the apex of the septum as in species of Gustavia, at the apex of the septum without a swollen placenta as in species of Grias, to a bilamellar placenta which runs the length of the septum as in species of Couroupita, to a bilamellar placenta at the base of the septum as in Lecythis pisonis, or to a placenta at the base of the locule itself as in species of Eschweilera.

The following descriptions and illustrations summarize our understanding of the diagnostic floral characteristics of each genus of New World Lecythidaceae.

Asteranthos (Fig 40)

The actinomorphic flowers of A. brasiliensis are apetalous. The showy, corolla-like structure is a corona of staminal origin. The calyx is also unique, being a circular rim with a crenate margin and marginal, widely separated, caducous teeth. Most New World Lecythidaceae have lobed calyces or, if the calyces are circular rims, as in some species of Gustavia and Grias, they are without marginal teeth. The anthers and filaments of A. brasiliensis are also diagnostic of the genus. The former are linear with longitudinal dehiscence, and the latter are without the apical constrictions so characteristic of other New World Lecythidaceae. The only other neotropical genus of Lecythidaceae with linear anthers is Gustavia, but in this genus anther dehiscence is apical rather than longitudinal. The ovary of A. brasiliensis is half-inferior, and the style is terminated by a capitate stigma with 5-8 radiate lobes.

Asteranthos has traditionally been related to Napoleonaea because both genera lack petals and possess coronas of staminal origin. Nonetheless, a careful morphological comparison of the flowers of the two genera is needed to determine whether these features result from common ancestry or convergent evolution.

Gustavia (Figs 9, 11A-E)

The flowers of this genus are actinomorphic. The staminal ring is well developed and ranges from 4 to 20 mm high. The stamens are borne on the

Eschweilera Flower

Was this article helpful?

0 0

Post a comment