The genus Dacrydium in Malaya (Gymnospermae)
When Corner described the genus Dacrydium in Malaya in 1939 he recognized four kinds, three species and a marked variety, but he expressed considerable doubt about their distinctiveness because the available specimens showed all degrees of variation of leaves between one species and another. He finally concluded that D. comosum was, in fact, unmistakable, because of its large needles, but that his variety subelatum of D. beccarii lay exactly between that species and D. elatum. During a recent collecting trip to Malaya, I was able to distinguish four distinct species and to identify the cause of the confusion which Comer described. The confusion in distinguishing Malayan species of Dacrydium results primarily from a misinterpretation of the form of D. elatum. This species is characterized by imbricate scale leaves in the adult form but with spreading acicular leaves in the juvenile form. Before I had seen living specimens of this species I was under die impression that the change in leaf form was abrupt and stated this in print (1969). There are many herbarium specimens with sharply contrasting juvenile and adult branches often actually attached to one another. In fact, there is a gradual change as a plant matures to shorter more adpressed leaves and different individuals mature at different rates. Trees with mature leaves, however, frequently bear occasional shoots with juvenile leaves making possible the collection of both juvenile and mature leaves attached on the same specimen. I myself collected specimens of this type before I realized what this collection strategy suggests to the herbarium user. Not only is there a gradual change in leaf form as a plant matures, but it is also common for a plant to become fertile before the transition is complete. Fertile specimens with spreading needles are well known throughout the range of this species including areas where it is the only Dacrydium species present. A male specimen, for example, Balansa 596 (K), comes from Tonkin; both male and female with spreading leaves as well as scale-leaved specimens were carefully assembled by Abbe & Smitinand (9459, 9460, 9461, A) from Phu Kradang in Thailand; and I myself collected a female specimen, de Laubenfels P532 (A, L, SING), at Ulu Kali in Malaya.
|Journal||Blumea: Biodiversity, Evolution and Biogeography of Plants|
|Rights||Released under the CC-BY 4.0 ("Attribution") License|
de Laubenfels, D. J. (1976). The genus Dacrydium in Malaya (Gymnospermae). Blumea: Biodiversity, Evolution and Biogeography of Plants, 23(1), 97–98.