EVOLUTIONARY TENDENCIES AMONG GYMNOSPERMS 429 



Cycadales, the primary root is polyarch. Even Araucaria, which is 

 exceptional in many respects, has been reported with six root poles, 

 although two is the usual number. In the Coniferales the reduction 

 in number of root poles is closely related to the reduction in number 



Fig. 462. — Diagrams illustrating the cotyledonary node of gymnosperms and its 

 vascular connections with the cotyledons : the lobes indicate cotyledons. — Prepared by 

 Sister Helen Angela. 



Series A, Cycadales: I, Dioon spinulosum (occasional); 2, D. edule (occasional); 

 3, D. spinulosum, Ceratozamia, Microcycas; 4, D. edule; 5, Zamia floridana, Cycas 

 spp. ; 6, Cycas siamensis; 7,C. Seemannii. 



Series B, Coniferales: 1-6, various species of the Pinaceae; 7, Libocedrus, Taxus, 

 Cephalotaxus. 



Series C, Ginkgoales, Gnetales, and exceptional Coniferales: /, 2, Ginkgo biloba/ 

 J, 4, Araucaria spp.; 5, Podocarpus; 6, 7, Gnetales. 



of cotyledons, for when the dicotyledonous condition is reached, the 

 root is diarch. Among the Cycadales, on the other hand, although 

 some have reached the diarch state, the characteristic root is tetrarch, 

 the intercotyledonary poles persisting after the dicotyledonous con- 

 dition is attained. An important consideration here, however, is 

 the fact that there is often a reduction in the number of poles in 



