Notes on Dipterocarps. {No. 9} On the differences in the seedlings between Balanocarpus maximus, King, and B. heimii, King
This note by I.H. Burkill describes the germination and early seedling morphology of Balanocarpus maximus, King, and contrasts it with B. heimii, King, using seeds collected by R. E. Holttum in Negri Sembilan in November 1922 (p. 218).
Burkill documents that B. maximus germinates by the radicle forcing 2–4 radiating cracks at the fruit apex, after which cotyledon expansion ruptures the fruit-wall along a single long crack whose position correlates with the placenta (p. 219). The cotyledons are nearly equal, stand parallel through life, and the young plant is purple with a single pair of first leaves (p. 220). By contrast, B. heimii has markedly dissimilar cotyledons packed one above the other, which become horizontal after germination, and is followed by four or five leaves in a cluster; the young plant is green (p. 221). A small experiment binding fruits with rubber rings confirmed that the fruit-wall is not dehiscent but is ruptured from within by cotyledon growth, consistent with earlier observations on Dipterocarps (p. 221). A summary table of the differences closes the note (p. 222).