44 ANATOMY OF THE GYMNOSPERMS 



Viewing these five genera collectively, their spirals conform 

 fully, in their occurrence and relation to progressive develop- 

 ment, to the general principles already stated, and especially 

 as formulated by De Bary. They possess no differential value 

 of generic rank with respect to Pinus and Larix, but they do 

 have such value with respect to Torreya and Taxus on the one 

 hand and Pseudotsuga on the other, the differentiation resting 

 upon their occurrence in the summer wood in the former and 

 their exclusion from that region in the latter. Were any ques- 

 tion to arise in this connection, it could be authoritatively decided 

 by the definite association of resin passages and fusiform rays 

 in Pseudotsuga. 



It only remains to determine how far such structural features 

 may be employed as a basis upon which to determine the general 

 phylogeny of the genera. Between Torreya and Taxus there is 

 very little upon which to base conclusions respecting sequence in 

 development, and it is apparent that both of these genera have 

 attained to nearly the same level. Such differences as do exist, 

 however, seem to point to the relatively though slightly inferior 

 position of Torreya as indicated by (i) the smaller angle in that 

 genus, and (2) the generally more compact spirals of Taxus. This 

 view, so far as it possesses phylogenetic value, appears to confirm 

 the conclusions respecting the relative positions of these two gen- 

 era as already determined upon the basis of external morphology 

 and stated by Eichler (15, 103). 



It is fairly clear, from the facts at hand, that all such spirals 

 as are to be met with in the higher Coniferales are to be regarded 

 as survivals of structures which gained greater prominence in 

 a more primitive state of development of the organism. They 

 do not, therefore, indicate simple parallelisms between plants 

 occupying a similar horizon in the scale of development, but they 

 rather direct attention to derivation from a common ancestry, 

 and, as previously pointed out (59, 255), they lead us to the con- 

 sideration that Torreya, Taxus, Pseudotsuga, Larix, and Pinus 

 represent different branches of a general phylum, - - undoubtedly 

 also including other closely related genera in which the spirals 



