LINUM USITATISSIMUM 



373 



fourth node are spirally arranged. (Fig. 189.) Tognini (15) 

 reported the phyllotaxy as %, but noted that there were frequent 

 exceptions to this plan even on one plant. Crooks (7), working 

 with the Bison variety, occasionally found three leaves in a whorl 



Fig. 188. Panicles of Bison flax showing flowers and arrangement of leaves. 

 (Courtesy Bureau Plant Industry.) 



at one of the lower nodes and observed cases in which leaves at the 

 sixth, seventh, or eighth nodes were bilobed. (Fig. 199, A.') In 

 some of these, the leaf was broad and cleft nearly to the base of the 

 lamina; in others, it was narrow with a very small cleft at the 

 apex. Ontogenetic studies indicate that such double leaves are 

 the result of the non-divergence in varying degree of two leaf pri- 

 mordia. 



