106 Inheritance in the Cowpea 



Small eye. These are the same types as were obtained by Spillman, 

 with the exception that the type Large eye spotted replaces the Large 

 eye. Large eye spotted is identical with the Large eye of Spillman 

 except that spots of pigment are usually found on the body of the seed. 

 It must be admitted that certain types would have been classified as 

 Large eye if a very close examination had not been made. Indeed it 

 happened that several pods had to be examined in some plants before 

 the pigment spots were seen. The type Large eye did not appear in 

 any of the crosses studied by the present writer. Large eye spotted 

 was classed as a Holstein. Actually it showed similar genetic behaviour 

 to Spillman's Large eye, and may be regarded as the heterozygote be- 

 tween Small eye and Holstein types e or f. 



The present writer does not wish to cast doubt upon the correctness 

 of Spillman's classification, for it is quite probable that the types with 

 which he worked were of different genetic constitution. 



A survey of the F2 results will render apparent the fact that the 

 Solids and Holsteins are in excess of the expected numbers while there 

 is a deficiency in the Watson and Small eye classes. Is the deviation 

 from expectation of genetic significance ? Assuming that the ratio 

 9:8:3:1 is the correct one, then all the Solids will contain both 

 Watson (W) and Holstein (H), and it is possible to determine which of 

 these factors is responsible for the deviation above alluded to. The 

 proportions in which W and H occur in the F2 families will be found 

 in Table VIII, from which it is clear that the deviation from the 

 9:3:3:1 ratio of Table VII is due to the fact that a greater number 

 of types with the Holstein factor are produced than are expected. The 

 ratio of W to w is close to 3 — I but the ratio of H to h is 4-9 to 1*0. 

 Thus from the F2 results it seems that in this cross the two factor hypo- 

 thesis of Spillman does not apply. 



TheF,. 



The Fs results are set forth in Table IX. A summary of them is as 

 follows : 



1. Solid may either (a) breed true, (6) segregate into Solid and Watson 

 (H : h = 4-8 : 1'O), (c) segregate into Solid and Holstein (W : w = S'l : I'O), 

 (d) segregate into Solid, Watson, Holstein and Small eye (H : h = 7*2 : 1*0 

 and W:w = 2-6:l-0). 



2. Watson segregates into Watson and Small eye {W : w = 2'6 : 1'O). 



3. Holstein segregates into Holstein and Small eye (H : h = 4*7 : 1'O) 

 or breeds true. 



4. Small eye breeds true. 



