﻿24 SCOTT, Early History of Seed-bearing Plants. 



within this plexus seem to have made rapid progress, and 

 in the Devonian period had already advanced to the rank 

 of well-characterised Gymnosperms, the remainder long 

 retained much of their primitive fern-like character, and 

 it was only in much later days, perhaps far on in the 

 carboniferous era, that they gave rise to seed-plants of a 

 more modern type (Cycadophyta). 



So far, then, as the great bulk of the Palaeozoic seed- 

 plants are concerned, their ultimate derivation from the 

 Filicinean stock seems clearly indicated by all available 

 evidence, and this conclusion, as we have seen, must be 

 extended to the whole of the Cycadophyta, both Meso- 

 zoic and recent. 



As regards the Coniferae, more difference of opinion is 

 likely to be found. Certain botanists, while accepting the 

 fern-origin of the Cycadophyta and Cordaiteae, have still 

 preferred to trace the Coniferae to a Lycopod ancestry. 

 Others have drawn a distinction within the Order, and 

 leaving the Taxaceae with the Fern-phylum, have assigned 

 the rest of the Conifers to the Lycopod line. 



It is only in the latest Palaeozoic deposits that true 

 Conifers ( WalcJiia and Voltzia being the chief genera) are 

 known to occur. Walchia appears to show most affinity 

 with the Araucarieae, while Voltzia has been compared 

 to the Taxodieae, of which the gigantic Sequoias are the 

 best known living representatives. We are not as yet in 

 a position to trace clearly the relations of these early 

 Coniferae to the Cordaiteae, but new light on the question 

 may be hoped for from Mr. Seward's work, now in pro- 

 gress, on Araucarian Conifers. The complete identity in 

 the structure of the wood between Araucarieae and Cor- 

 daiteae (which for many years led to the inclusion of the 

 latter among Coniferae) can hardly be without significance. 

 This type of wood, characterized by the arrangement of 



