GABRIELLE L. C. HOWARD. 89 



explain why there is a limiting effect without true correlation. 



The study of the venation has yielded some most interest- 

 ing results and has demonstrated very conclusively the existence 

 of homozygotic combinations with values between those of the 

 parents. Table XXII gives the results of the cross Type 9 x 

 Type 51. The Fi is intermediate as usual, and the Fg covers the 

 combined range of the parents. In the F3 only one culture, 

 167, appeared to be uniform, and this had a mean venation 

 slightly greater than Type 51, The limits of variation were, 

 however, very different in the various cultures, and two 

 cultures in which these overlap very slightly, 738 and 694, 

 were continued. From culture 738, with a range of 40° to 70° 

 in the F3, the plants with the lowest and highest angles were 

 grown in the following year, as well as four others. In the F4 

 generation two cultures 19 and 96 were uniform with an average 

 venation of 50°, and a range of 40° to 55°, two others 58 and 

 81 were uniform with an average of 60°, while one culture 15 

 resembled the parent culture 738 in every respect. The 

 behaviour of the other culture is not very clear; it may 

 indicate another homozygotic combination at 55°. Thus 

 two homozygotic combinations, representing 50° and 60° 

 respectively, have been isolated, one of which is a replica 

 of one of the parents, the other is new. The F^ cultures 

 of 694 do not give such definite information, but they indicate 

 the occurrence of another homozygotic combination 65°-70°, 

 and it is possible that 694-1 represents this. 



The cross between Type 16 x Type 35 (Table XXIII) gives 

 very similar results to those described before. All the cultures 

 (four) with a venation of 50° or 45° have bred true ; one culture 

 of which the parent plant had a venation of 60° has also bred 

 true, and here again is the formation of a homozygotic 

 combination intermediate between the two parents. Cultures 

 200 and 8 are possibly uniform with an average of 75°, again 

 a novum. The other cultures are apparently heterozygotes 

 splitting within different limits. 



