164 CONIFERALES (RECENT) [CH. XLIII 



arboreum ; Dacrydium Bidwillii^, D. Franklini and D. araucarioides 

 (fig. 708, B) recall some species of Lycof odium, and D. cupressinum^, 

 a dimorphic species, may simulate Lycopodium tetragonum. The 

 long, linear, distichous leaves of some species of Podocarpus and 

 Cephalotaxus might, as fossils, be confused with the pinnate leaves 

 of Cycas ; further, as Bommer points out, the leaves of Podocarpus 

 Blumei resemble those of Agathis and the seeds are similar to those 

 of Dehaasia media (Lauraceae). The Cupressus type of shoot 

 occurs in Baccharis scolopendra as in other Dicotyledonous plants 

 (fig. 711). The presence of a midrib in a linear Taxus-hke leaf 

 though usually easy to recognise is not always obvious, e.g., in 

 Torreya nucifera the midrib cannot always be distinguished on 

 the upper face of the leaves. The recurrence of a similar habit 

 in many Conifers renders difficult the identification of vegetative 

 shoots, particularly as in fossil specimens the precise method of 

 attachment of the leaves, their texture, and other features are 

 frequently unrecognisable. The tendency to dimorphism in 

 many genera is another difficulty: examples of dimorphic shoots 

 are afforded hj Dacrydium laxifolium, D.Kirkii, D.elatium (fig. 708, 

 A), Juniperus chinensis, Araucaria excelsa, Callitris glauca, Podo- 

 carpus cxi'pressina^ , P. imbricata. Thuya occidenialis, etc. Allusion 

 has been made to the considerable variation in the length of leaves 

 on a single branch of different Conifers : in such a form as Crypto- 

 meria jajmnica var. spiralis Sieb. and in similar varieties of other 

 genera the spirally twisted leaves, reminding one on a small scale 

 of the 'wind-blown' Acanthus leaves on a Byzantine capital, 

 constitute a feature which might be regarded as of taxonomic 

 importance. The investigation of the cuticular membranes of 

 Conifer leaves, as yet but little attempted, may supply useful 

 criteria as in the case of Cycadean fronds. 



1 Pilger (03) fig. 4 A. ' Kirk (89) Pis. svin., xix. 



' Bennett and Brown (52) PJ. x 



