222 Mendelian Inheritanvc In lirvoiiia dioica 



4. Habit and foliage. 



Differences relating to these features are evidently complex in origin 

 and have not been adequately studied for complete analysis. 



The following points have been determined : 



(a) Crossing leads to the production of a number of new types 

 in the second generation. 



(6) Segi'egation ocon-s involving the reappearance of the 

 original characters of the grandparents in the F.^ generation. 



(c) The number of factors concerned in the determination of 

 leaf-shape is small— possibly two. 



5. The experiments on Bryony emphasize once more the need for 

 caution in the sub-division of existing species without recourse to 

 breeding tests. 



A number of segregates showing morphological differences due to 

 new combinations can evidently arise from the intercrossing of a few 

 stable types within the limits of a so-called species. 



The stability of these new forms can only be tested by breeding, 

 and the extreme types among them may be connected by an almost 

 continuous series of transition forms. 



Bedford College, 



University of London. 



University College, 



Reading. 



