140 THE COTTON PLANT IN EGYPT CHAP. 



be under the control of a simple pair of allelomorphs, so 

 far as evidence is available. 



This presentment does not exhaust the possibilities, for 

 a family of King Upland, grown from seed of a selected 

 plant, showed itself to be a hybrid in this resp'ect. The 

 anther colour of the selected parent was pale lemon, which 

 broke up on self- fertilisation into 24 lemon : 8 buff. The 

 latter have since bred true, as have some of the lemons. In 

 this case the pair was simple, with dominance of more 

 colour over less colour. 



Hirsuteness. The hairiness of the plant involves a 

 number of factors ; one type of hair may be confined to 

 the leaf-lamina, another to the veins, another to the stem, 

 and so forth. During our studies of this character in 

 cotton we have examined only the petiole of the leaf. 



The Egyptian cottons have glabrous petioles, the 

 American Upland petioles are more or less hirsute, and 

 the Ft petiole is almost glabrous. The author's first 

 published mention of this character 5 ' 8 stated that the 

 glabrous form was completely dominant. In almost all 

 other plants the reverse is true, and further complications 

 were expected when Mr. Holtou discovered that a few 

 long but scanty hairs were present on the Fj petiole. 



Early classifications of F 2 and F 3 in which glabrous and 

 intermediate were grouped together as non-hirsute, gave 

 ratios of "non-hirsute: hirsute" as 111 : 37, 58 : 17, 

 43 : 9, &c. On cultivating some extracted hirsutes in F 4 

 we found six out of seven breeding true to hirsuteness, 

 while one broke up, giving 31 : 8, the eight being of the 

 F a type. Moreover, we found that the extracted forms 

 differed in the length and density of their hairs, and that 

 segregation in this respect was indicated within the limits 

 of the hirsute group. 



A very careful classification Avas then made on the 

 F 2 of another Upland-Egyptian cross, which gave the 

 following results : 



