130 



Gates, Tetraploid Mutants and Chromosome Mechanisms. 



Table V. 

 Pollen grains of 0. gigas and other races. 



From the accompanying tables (V. and VI.) it will be seen that 

 in typical O. yigas Italy a fluctuating amount of the pollen, probably 

 in most cases much over fifty per cent, was non-functional. Of the 

 grains having a normal appearance, from 2 6 per cent, were 3-lobed, 

 86 to 90 per cent, were 4-lobed, while about 7 per cent, had five 

 or more lobes. In the individual (No. I. 4) having smaller flowers, 

 leaves and stature, the amount of sterility is about the same, but 

 the number of triangular grains was regularly about 25 per cent, 

 in all the flowers examined (Table VI), grains having five or more 

 lobes only numbering about 1.54 per cent. Thus in every case 

 the ratio of 4-lobed to 3-lobed grains in this plant was found to 

 be approximately 3:1. Whether this Mendelian ratio may have 

 any significance as such is not at present clear. Its chief interest 

 lies in the fact that the smaller size of the plant organs is accompanied 

 by this peculiar behaviour of the pollen. A count of the chromo- 



