CONIFERALES 



323 



radial section. The pits are neither crowded nor alternating as 

 in the wood of the adult. An examination of the organization 

 of the seedling in the living representatives of the araucarian 

 conifers therefore justifies the view that the ancestral forms did 

 not possess crowded pitting. Precisely similar conditions are 

 found in the cone, for here the pits in the tracheids nearer the 

 primary wood lack the crowded and alternating disposition of 

 the mature vegeta- 

 tive wood of the 

 genus. But a still 

 more important 

 feature is pre- 

 sented by the 

 organization of the 

 wood of the ovu- 

 liferous cones of 

 the living A gat his 

 and Araucaria. 

 Fig. 233 shows a 

 longitudinal radial 

 view of the second- 

 ary wood of Arau- 

 caria Bidwillii in 

 the vicinity of the 

 protoxylem. The 

 pits show a very strong tendency to opposition in arrangement, 

 and are certainly not angular by mutual contact, as is often the 

 case in cordaitean woods. The most interesting feature shown 

 by the figure, however, is the presence of bars of Sanio such as 

 are entirely lacking in the adult vegetative wood of existing species 

 of the araucarian conifers. As a consequence of the situation 

 revealed in the conservative reproductive axis of the araucarian 

 conifers, we are justified in assuming that the absence of bars of 

 Sanio and the presence of alternating pitting are not primitive 

 features of the organization of the wood of the subtribe, and 

 consequently cannot be brought into court to prove its cor- 

 daitean affinities. The evidence, in fact, must be read in exactly 



FIG. 232. Longitudinal section of the wood of the 

 seedling in Agathis australis. 



