IN THE TROPICS : III. 



149 



No. 



I 



2 



3 

 4 

 5 

 6 



Total 1,063 



Table 39. 



Totai. 



438 

 459 

 427 

 404 

 350 

 188 



Per cent. 

 Whit°. 



47-0 

 45-0 

 48-2 

 46-3 

 44-9 

 52-8 



1,203 



2.266 



46-91 



Per cent 

 Blue 



53 

 55 

 51 

 53 

 55 

 47 



53-09 



The particular cob chosen for further examination (No. 2) 

 had 55 per cent, of blue grains. If blue had been dominant 

 in every case we should have expected the proportion 75 

 per cent, of blue grains to 25 percent, of white. Hence, as it 

 is. only 25 out of 45 white grains should be pure recessive 

 homozygotes. 



F3. 



On sowing the white grains and exposing the emasculated 

 plants to the pollen of white dent. 36 plants out of 63 were 

 found to bear either exclusively white grains (or in 7 cases 1 

 or 2 blue grains in addition to white), whilst 27 plants bore 

 from 1 to 36 per cent, of blue grains. Thus 57 per cent, of the 

 whites in F 2 , or a proportion of 26 out of 45, were shown by 

 an examination of their progeny to be pure recessives ; 

 that is, 26 percent, of the total number of grains of F 2 , which 

 comes very near the Mendelian 25 per cent. 



Table 40 shows the actual proportion of blue and white 

 grains among the offspring of white grains in F3 : — 



