274 GYMNOSPERMS 



endarch protoxylem. There is no centripetal xylem at any time, the 

 change from an exarch to an endarch position of the protoxylem being 

 due entirely to rotation. 



The stomata on the hypocotyl of Piniis cdiilis seem to be a little 

 dilTerent from those on other parts of the plant; and those on the 

 cotyledons and leaves are so different from each other that, taken 

 separately, they might seem to belong to different species, or even 

 different genera. The hypocotyl of conifers would seem to be a good 

 place for a thorough study of comparative anatomy. 



