216 MendeUan Inheritcmce in Bryonia dioica 



the 7 + 7 arrangement, a majority always do so, and practically all 

 shoots on the jilant will be found to possess more than ten bundles. 



Records and careful drawings of serial sections through successive 

 nodes and internodes have not provided any simple clue as to the 

 significance of the 7 + 7 an-angement as compared with the other, and 

 the condition is evidently a complicated one anatomically. 



Fig. .5. li. (iioicu, vars. B and G. Transverse sections of stem internodes ; u and b 

 from variety B; c from variety G. 



Camera lucida drawings. 



The branching and anastomoses of the vascular strands become very 

 complex at the nodes, and a detailed investigation of this region has 

 not proved of any service in the investigation. A very short distance 

 above or below the node, the arrangement of bundles typical for the 

 variety is re-established. 



Genetical hehavioxir. 



If i^ be a factor conferring a capacity to increase the number of 

 bundles beyond ten, then the facts would be satisfied if F were dominant 

 over / (a capacity for increasing the number of bundles up to but not 

 beyond ten). 



Theoretical. 



FF (7! plant) x ff (G plant) 

 I 

 F^ all Ff 



Experimental. Of four plants from this cross, three had 14 bundles, 

 one had 11-13 bundles. 



