CONIFERALES 



331 



of parenchymatous elements. In still other species the short 

 tracheary elements ordinarily called transfusion cells were much 

 less well developed. It is the remarkable genus Prepinus, however, 

 which provides the most important evidence for estimating the 

 bearing of the anatomical organization of the leaf on the problem 

 of evolution of the genus Pinus in particular and that of the 

 Abietineae in general. In Fig. 240 is shown the transverse section 



FIG. 239. Leaf bundle of Pinus Strobus 



of the leaf in P. statenensis . The outline is angular because of 

 mutual contact with other and surrounding leaves of the fascicle. 

 In Prepinus the growing point of the short-shoots persisted as it 

 does in the living Ginkgo, and the fascicular leaves, instead of being 

 few and definite in their number, were indefinitely numerous. 

 It is interesting to note in this connection, however, that, although 

 in the true Pinus of the Cretaceous the number of leaves in the 

 fascicle was few and fixed as in modern forms, nevertheless the 

 growing point of the short-shoot persisted indefinitely and did 

 not disappear at an early stage, as in the living representative of 



