Inheritance in Gametophytes 



129 



considered. These could also coexist in a gametophyte 

 but not to the same degree as in a sporophyte. If three 

 cumulative factors were active in a sporophyte, it is 

 evident that there could be gradations as indicated 

 by fig. 30. If, on the other hand, three cumulative 

 factors were active in a gametophyte there could only 

 be the gradations indicated by fig. 31. Thus the 

 behavior of cumulative factors in sporophytes and 

 gametophytes would differ quantitatively; there would 



3 Doses 







2 Doses 



a 



- - 



A" 1 







1 Dose 



Dose 



GAMETOPHYTE 



FIG. 31. Diagram showing how the cumulative factors of fig. 30 

 could produce only four different quantitative classes in the gameto- 

 phyte generation. 



not be so many gradations in gametophytes for the 

 same number of factors involved. 



As a general conclusion, therefore, it may be said that 

 a knowledge of inheritance in gametophytes would test 

 our theoretical mechanism for inheritance in sporo- 

 phytes. 



There is another important value to be secured from 

 a knowledge of genetics in gametophytes. In the study 

 of genetics in the sporophytes of the higher plants we 

 are dealing with very complex organisms. Attention 

 has been called to the possibilities of parthenogenesis 



