The Mode of lulieritance of Semi-Sterility in the OffspriDg of Certain Hybrid Plants. 327 



Considering the increasing proportion of semi-sterile plants, it may 

 perhaps be questioned whether the plants which had not flowered by 

 October 13 (or which flowered before, l)ut whose flowers were not 

 seen), if included, would have altered the ratio from 1:1. There were 

 only 30 of these, 22 with black tomentum (which plants are usually 

 late), and 8 with white pul»escence. Omitting all the earlier black 

 plants, and considering only those with white pubescence on buds, leaves, 

 etc., the numbers are 157 plants with normal, and 164 plants with half- 

 aborted pollen. Tills is evidently the ratio 1:1. (The black plants 

 which flowered in time to be examined consisted of 23 with normal, 

 and 31 with half-aborted pollen.) 



The plants were grown in rows 320 feet long, with 40 plants in 

 each row, each supported by three four-foot poles. Some seeds did not 

 grow to mature plants. It will be instructive, since only 40 seeds (or 

 less) of each line were sown in the next generation, to compare the 

 results for each row. Thus we may see what variation in the ratio 

 may be expected for the plants from 40 seeds. 



Row 1 

 Row 2 

 Row 3 

 Row 4 

 Row 5 

 Row 6 

 Row 7 

 Row 8 

 Row 9 

 Row 10 

 Row 11 

 Row 12 



To' 



Plants with 

 normal pollen 



11 



18 



1.5 



16 



12 



21 



13 



15 



14 



17 



10 



IS 



Plants with half- 

 aborted pollen 



21 



11 



18 



1.3 



13 



11 



20 



17 



19 



15 



22 



15 



Differences 



- +10 



- +3 



- —3 



- +1 



- — 10 



- +7 



- +2 



- +Ö 

 _ 2 



- +12 



- —3 



,als 180 



195 



+ 15 



Hence it is evident that it cannot be told from one row of only 40 

 seeds whether the ratio is 1:1, or not. 



A ratio of 1:1 is an uncommon Mendelian ratio in the progeny 

 of a selfed hybrid. But there is, I think, no need to consider this a 

 ratio among zygotes, as are the ordinary Mendelian ratios in the second 

 generation of this and other crosses. For this distinction of fertility 

 and semi-sterility is, I repeat, an affair of the haploid generation, and 

 only affects the diploid generation secondaiily. There is no question 

 of dominance or recessiveness, for the character simply does not appear 



