Oenothera Lata. 



405 



ficial growth of the leaf parenchyma in proportion to 

 that of the nerves; but perhaps we must seek deeper 

 for it. 



It is not, however, easy to see how the same cause 

 can make the stigma abnormal, the fruits small and the 

 pollen sterile. On the other hand if we suppose that each 



Fig. 89. Oenothera lata. A, a radical leaf. B, the bract, 

 from the axil of which the lowest flower arose. C, apex 

 of a small lateral branch. A', B', C, the corresponding 

 parts of O. Lamarckiana diminished the same amount. 



of these characters is due to a distinct cause we have no 

 means of accounting for the fact that they always appear 

 together and never one at a time : for this clearly could 

 not be due to chance. 



I imagine that the cause of every such a mutation 



