Dacrydium

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Dacrydium

Description

Usually dioecious shrubs to large trees as much as 40 m tall. Bark hard and smooth with fissures and breaking off in plates, with numerous small lenticels, reddish brown and weathering to gray, slightly fibrous within. Leaves on mature plants more variable among the species, from small keeled adpressed scales 1 mm long to linear leaves or needles as much as 2 cm long, straight to strongly incurved at the tip, tetragonal in cross section or keeled on the dorsal side and flat or even strongly concave on the axial surface, in some cases as much as six times as wide as thick, apex blunt to narrowly acute. Where adult leaves differ sharply from the juvenile leaves the transition may be gradual or almost abrupt and juvenile shoots mixed with adult foliage are often seen. Leaves spirally placed. The solitary ovule of a fertile bract is cupped by an epimatium which represents the fertile scale and which lies between the ovule and the subtending fertile bract. Seeds become dark brown and have the same shape as those of Phyllocladus.

Distribution

Asia-Tropical: Borneo present; Jawa (Jawa present); Lesser Sunda Is. present; Malaya present; New Guinea present, Australasia: Tasmania (Tasmania present), New Caledonia present present, New Zealand present present, Pacific: Fiji (Fiji present), Southeast Asia present, southern Chile present
In all 25 spp., from Southeast Asia through Malesia (not in Java and the Lesser Sunda Islands) to New Caledonia and Fiji, Tasmania, New Zealand and southern Chile. Within Malesia (14 spp.) the greatest variety is found in Borneo (7 spp.), followed by New Guinea (6) and Malaya (5), while both New Caledonia and New Zealand have 4 endemic species each. .

Taxonomy

The genus can be loosely divided into four subgroups (those with scale leaves, those with leaves much wider than thick, those with broadly triangular apices to the microsporophylls, and those with none of these characters) each of which is widely distributed in Malesia and somewhat beyond. The seemingly most primitive forms are concentrated in New Zealand with one in Tasmania.

Notes

Dacrydium includes species whose leaves, progressing from acicular juvenile forms to mature scales, correspond to common early Mesozoic fossil foliage forms. Similar examples are also found in other families. A primitive clustering of pollen cones is found in the genus but the seed cones show an intermediate stage of development for the family. The most primitive seed cone form in Dacrydium is a rather loose structure with bracts resembling foliage leaves, rather than the compact cone of several other genera and of preceding fossil conifers. Other seed-bearing structures are further reduced to fewer fertile units and an exposed subterminal seed placement anticipating the more formal structure in the more advanced genera of the family. The rotation of the seed as it matures is a specialized trait.

Citation

DE LAUB. 1969: p. 282. – In: J. Arn. Arb. f. 1 -5
EICHLER 1889 – In: E. & P., Nat. Pfl. Fam. 2. p 106
PILGER 1903: p. 43. – In: Pfl. R. f. 4-6
HENKEL & HOCHSTETTER 1865: Synop. Nadelhölz. p 405
QUINN 1982 – In: Austr. J. Bot. p 311
FOST.f. 1972 – In: Fl. Nouv. Ca-léd. et Dép. p 17
RICH. 1826: Comm. Bot. Conif. & Cycad. p 127
GAUSSEN 1974: p. 11. – In: Gymn. Act. & Foss. f. 681-697, t. 85-87
ENDL. 1847: Syn. Conif. p 224
Corner 1939: p. 239. – In: Gard. Bull. S. S. t. 5-10
FOST.f. 1786: Fl. Ins. Austr. Prod. p 92
FLORIN 1931: p. 248. – In: Kongl. Svensk. Vet. Ak. Handl. f. 71
FOST.f. 1926 – In: E. & P., Nat. Pfl. Fam., ed. 2, 13. p 239
VAN ROYEN 1979 – In: Alpine Fl. New Guinea. p 33
QUINN 1982: p. 316. – In: Austr. J. Bot. f. 7-8
BENTH. & HOOK.f. 1880 – In: Gen. Pl. p 433
PARL. 1868 – In: DC., Prod. 16. p 493
ex LAMBERT 1807: Gen. Pinus, ed. 1. t. 41