THE GYMNOSPERMAE : CONIFERALES AND TAXALES 695 



The cotyledonary bundles in some species of Pinus are mesarch, that is to 

 say, some centripetal xylem is present, which is characteristic of the extinct 

 Gymnosperms. On the other hand this is absent in the Araucarians. 



Another primitive character in Araucaria is the persistence of the leaf 

 traces, even in the wood of old trees, while the elaborate resin-canal system 

 oi Pinus might be regarded as an advanced type of structure. 



The confusing picture presented by such apparently contradictory 

 evidence is a salutary warning against too great a reliance on anatomical 

 features in questions of evolutionary history. It is absurd to assume, as has 



Fig. 698. — Pinus sylvestris. Longitudinal radial 

 section of secondan' wood stained to show Rims 

 of Sanio. 



sometimes been done, that certain supposedly " primitive " features of 

 structure must necessarily stamp the whole plant as primitive, for the juxta- 

 position of old and new characters is by no means uncommon and might 

 indeed be expected from the degree of independence in development exhibited 

 by plant structures. 



Whichever may be the oldest group of the living Coniferales the con- 

 nection of the order as a whole with the Cordaitales and through them with 

 the Pteridosperms is scarcely open to doubt, and we must look to the fossil 

 record for the final solution of the obscurities remaining in the problem. 



Taxales 



The order Taxales, as we shall here regard it, consists of a single family, 

 Taxaceae, containing three genera, Taxiis, Cephalotaxus and Torreya. The 

 Podocarpineae, which were formerly included in this group, are now 



