210 Detection of Secfregation of the Pollen of Rice 



bears a mixture of starchy and glutinous grains. These give rise in F., 

 to three groups of plants, bearing respectively — all starchy grains, all 

 glutinous, and a mixture of starchy and glutinous as in t\. Those bear- 

 ing all starchy or all glutinous grains breed true to these characters in 

 Fs, whereas those which bear the mixture give the three groups again 

 •mF,. 



The mixture of grains on an F^ plant should give a simple 3 : 1 ratio 

 of starchy to f/lutinout>. This ratio is approached fairly nearly in the 

 numbers recorded, though there is always a slight excess of starchy. For 

 nine plants, each giving about the same ratio, the following total figures 

 were obtained : 



In F.J the three groups of plants would be expected to give a 1:2:1 

 ratio of starchy : miwture : glutinous. In the families so far raised there 

 is a very considerable departure from this ratio as shown by the following 

 figures : 



It appears most probable that the single factor explanation of the 

 difference between starchy and glutinous is correct but that some dis- 

 turbing influence affects the ratios in F~^. There are a number of possi- 

 bilities in this direction and some of these are being investigated. 

 Certain preliminary results suggest that differential germination and 

 dying-off may be responsible. 



Pollen Binwrphisin. 



In searching for some explanation of the F.j ratios an examination 

 was made of the pollen on F^ plants. With a view to distinguishing the 

 two genetic types the pollen was treated with iodine. The result was 

 most satisfactory — two distinct types became evident, one giving the 

 dark blue reaction of ordinary starch and the other the reddish reaction 

 of amylodextrine. With iodine solution of the right strength a very 

 sharp distinction can be obtained since the starchy grains become dark 

 blue whilst the others remain only yellowish. 



Pollen from the two pure parents was then examined in iodine 

 solution. The starchy parent gave only the blue type of pollen ; the 

 glutinous parent gave the reddish type. 



