CONIFERALES 



347 



the Abietineae. Here resin canals are normally absent, not only 

 in the structure of the wood, but also in the other tissues of the 

 stem. In the root of the genus they occur in the primary wood; 

 and in the cone and leaves, in the tissues of the cortex. This 

 distribution of resin canals is of course entirely in accord with 

 the general principles of evolutionary anatomy. Tsuga, however, 

 differs markedly from Taxus in the degree of obliteration of resin 

 canals, since these structures here persist in conservative regions, 

 while in the latter genus 

 they have entirely disap- 

 peared. In Cephalotaxus 

 resin canals are well devel- 

 oped except in the wood, 

 but are apparently not 

 susceptible of reversionary 

 recall in ligneous struc- 

 tures. 



It will be obvious from 

 the description of the re- 

 productive and vegetative 

 organization supplied in 

 the two preceding para- 

 graphs that so simple a 



FIG. 253. Transverse section of the wood 

 of the root in Taxus cuspidata (after Bliss). 



type as the genus Taxus 

 cannot, according to the well-established principles of anatomy, be 

 regarded as a primitive form. Its acceptance in this capacity by 

 the earlier and philosophical taxonomy is shown on inductive evi- 

 dence to be entirely unjustified. It appears on the basis of the 

 facts at present available that the Taxineae are a reduction series 

 in which the oriental Cephalotaxus among existing genera occupies 

 the lowest position, while Taxus represents the summit. It is 

 further obvious that the absence of wood parenchyma is not a 

 primitive feature of organization of the group. If it be admitted 

 that longitudinal parenchymatous elements primitively character- 

 ized the organization of the wood, a derivation from the same 

 stock as the Podocarpineae is plainly indicated. This conclusion 

 is justified by the consideration of the young ovuliferous cone in 



