318 
LOOK : STUDIES IN PLANT BREEDING 
The blue grains are to be regarded as the result of acci¬ 
dental xenia. Taking all the plants together the result is 
50*1 per cent, of white and 49*7 per cent, of yellow, out of 
a total of nearly 4,000 grains. 
The accuracy of the sampling can be tested by growing 
another generation (F 3 ) and again pollinating by the 
recessive. The yellow grains should all be heterozygotes 
and again produce 50 per cent, of yellow grains and 50 per 
cent, of white, whilst white grains should produce nothing 
but white. 78 white and 126 yellow grains were sown. 
These were taken from the finest cob, No. 5, which had 
yielded 46*6 per cent, of yellow grains. The recessive form 
used in this case was a white Dent variety—“ Boone County 
From the white grains 59 plants produced fruit, and 44 of 
them produced exclusively white grains (F 3 ). The remain¬ 
ing 15 cobs showed white grains with the following 
exceptions 
1 cob showed 2 blue grains 
6 cobs had each 1 yellow grain ... ••• 
6 „ „ 2 yellow grains... ••• 
1 „ „ 3 „ ... - 
1 „ „ 6 „ ., ... ... 
All the plants upon which these yellow grains appeared 
grew close together near one end of a row, and it seems 
clear that some “yellow” pollen had escaped from a plant 
in the next row but one. The purity of the extracted 
recessives is therefore fully established. 
Of the offspring of yellow grains of the same generation 
(F 2 ) one cob was gathered from each of 96 plants. One of 
these cobs showed 32 blue grains, in addition to 253 yellow 
and 205 white grains; and the first mentioned are doubi 
the result of a previous accidental cross by blue, 
remaining 95 cobs showed, without exception, yellow 
white grains only (F 3 ) in the proportion approximately of 
lav 
