Notes on Dipterocarps. {No. 1} The seedling of Anisoptera cosgata, Korth
This note by I. H. Burkill describes the germination and early seedling development of Anisoptera costata, Korthals, based on observations of two wild specimens in the Botanic Gardens, Singapore, that flowered in April 1916.
Summary
Burkill documents the germination sequence in detail: the radicle emerges and anchors, then the hypocotyl straightens to pull the cotyledons from the capsule. The two cotyledons are markedly unequal in size and shape, the larger being four-ridged on the back and the lesser sagittate-reniform; he corrects Brandis and Gilg’s claim that great petiole elongation is a general character of the order, noting it is specific to Dipterocarpus (p. 44). The cotyledons must reach light to function, and seedlings die or languish if imprisoned (p. 44). A whorl of four leaves follows, in which two contiguous leaves (those over the lesser cotyledon) are commonly larger than the other two; this inequality persists through life (p. 45). Burkill compares these features with Shorea, which has equal, sagittately bilobed cotyledons and paired first leaves rather than a whorl of four (p. 46). Microscopically, the petioles of the whorled leaves show no important structural difference from the fifth leaf, both exhibiting a ring of sclerenchyma enclosing phloem and xylem with associated resin ducts, and a pulvinus region where the sclerenchyma is absent (p. 47). Burkill concludes that the middle of the petiole, rather than the pulvinus as Brandis had suggested, offers the more promising site for studying generic characters (p. 48).