W. Nkilson Jonks and M. Chevelv Kavner :i21 



coiiiiectL'd with tho existence of faoultalive [jartheiiDgeiiesis and is 

 comparable to that observed in Alchenulla, Hieraciinu, etc. 



This possibility is of course not excluded by our results, but it seems 

 unlikely that it is the most important cause at work. 



Nothing is known at present of the cytology of parthenogenesis 

 in Bryony — if it occurs — and seeds produced partheiiogenetically are — 

 according to Bitter and Focke — borne but rarely and in small numbers. 



It seems, therefore, more reasonable to regard the varietal forms 

 described as hiuti/pes which, on crossing, give rise to fresh types by 

 'shuflfling' and recombination of characters according to Mendelian 

 laws (II). 



Summary. 



The paper is concerned with the genetical behaviour of certain 

 differentiating features in two distinct strains or varieties of Bryonia 

 dioica. 



The results obtained from breeding experiments may be sununarized 

 as follows : 



1. Bloom OH the berry. 



Absence of a vjaxy bloum from the ripe berries of one variety 

 behaves as a simple dominant to presence of wa.ry bloom on the berries 

 of the other variety. 



Presence and absence of bloom behave as a pair of simple allilo- 

 morphic factors. 



2. Number of carpels in $ floiver. 



The proportion of two-carpellary to thrre-carpellary Howers, as 

 evidenced by the number of stigma-lobes and of [jlacentae in the 

 ovary of the flower, in families of plants produced by crossing the two 

 varieties, can be interpreted by assuming the co-operation of two 

 factors. 



3. Anatomy uf stem. 



The number of vascular bundles in transverse sections of the stem 

 of one vai-iety is typically 10 (.5 +.5), and in the other typicall}' 14 

 (7 + 7). 



The capacity to increase the number of bundles beyond ten behaves 

 as a simple dominant to absence of such capacity. 



