H. Martin Leake and B. Ram Pershad 



The 9 factor. 



Parents possessing a full pink colour in the petal invariably breed 

 true and are therefore pure for the factor, or factors, developing that 

 marginal colour. 



The light pink, VL and LP, forms are impure, and the figures which 

 follow indicate that a single factor only is concerned. To this factor we 

 have given the designation P, and the VL and LP forms, therefore, 

 have the constitution Pp. 



In the case of three of the crosses the ^i and the impure F2 plants 

 were of the form VL, which, as has been stated, is with difficulty dis- 

 tinguished from the pure white. For this reason the count has, in 

 these cases, been made jointly to include both forms. 



The figures given for these 63 families illustrate a feature which, as 

 it is one which will have to be borne in mind in considering all the 

 results which follow, we may refer to here, though the matter will be 

 dealt with later in more detail. Stated briefly, it is the existence of a 

 correlation between the presence of the factor which develops the pink 

 marginal colour and the length of the vegetative period of the plant. 

 When the factor, which we have termed P, is present, a marked 

 shortening of the vegetative period occurs and this phenomenon intro- 

 duces certain practical difficulties which cannot be disposed of altogether. 



In agreement with the common practice the seed is sown on land 

 which has been irrigated and ploughed, and germination consequently 

 takes place on a rapidly decreasing moisture. Under the conditions of 

 experiment, a variable proportion of the seed will fail to germinate on 

 sowing, but will do so on the first irrigation of the growing crop. Such 

 plants constitute a second growth, of which only the more rapidly 

 maturing plants will flower before the dry winds of the early hot 

 weather kill all plants still in the vegetative condition. This pre- 

 flowering death-rate is consequently greatest in those late maturing 

 plants which do not carry the factor P, and counts thus show a 

 deficiency in the number of such plants. This source of error cannot be 



