Varietäten, Descendenz, Hybriden. 213 



altogether understood, but it is possiblc to frame a provisional 

 hypothesis consistent with the facts as yet observed. 



Various cases of gämetic coupling and repulsion have been met 

 with. In the case of the factors for magenta-colour and Short style, 

 the occurrence of coupling or repulsion has been proved to depend 

 upon the way in which the cross is made; the heterozygote resulting 

 from the union MS X ms shows coupling, that resulting from the 

 union Ms X m S shows repulsion between the two factors. The partial 

 coupling between the factors for green Stigma and magenta colour 

 does not conform to any System yet known, the two middle terms 

 of the F., series being larger, relatively to the end. terms, than 

 would be expected even if the coupling were of such a low order 

 as 3:1:1:3. 



Other characters dealt with in Gregory's paper are hetero- 

 stylism, the shape of the leaves and the characters of the leaf- 

 margin, the habit of the plant, double flowers, and characters of 

 the "eye" of the flower. The inheritance in these cases is, for the 

 most part, of a simple type. In the case of heterostylism there is, 

 however, a small, but apparently steady, divergence from the nu- 

 merical ratios which theory leads us to expect the various forms 

 of experiment to give. R. P. Gregory. 



Leake, H, M., Studies in Indian Cotton. (Journ. Gen. I. p. 

 204—272. 2 pl. (1 coloured) and text-fig. 1911.) 



The Indian Cottons fall into two groups, distinguished from 

 one another by the type of secondary brannhing. Arising from the 

 main axis, which is always a monopodium, the secondary branches 

 may be either monopodia or sympodia. The type in which all the 

 secondary branches are sympodia has not been observed; never- 

 theless, in pure races, the number of monopodia produced at the 

 base by a sympodial plant is limited , and the monopodial and sym- 

 podial types stand in sharp contrast on this point. 



The characters which have been dealt with are those of colour, 

 the form of the leaf, the type of branching and length of vegetative 

 period, and the presence of glands on the leaf. 



Colour. The colour characters which have been dealt with are 

 1) a red anthocyanic pigment which affects the whole plant: stem 

 leaves and flowers, 2) the yellow pigment of the petals. The hetero- 

 zygous red coloured plant has a less intense coloration than the 

 pure pigmented race. Yellow pigment is fully dominant, the hetero- 

 zygous yellow being indistinguishable to the e}^e from the pure 

 race; the yellow may be füll or pale, füll yellow being dominant 

 to pale yellow. The factors for these characters undergo indepen- 

 dent segregation and the numbers which have been obtained in 

 F 2 from various crosses are in accord with simple Mendelian 

 expectation. The various types of flower produced bjr the different 

 combinations of red and yellow pigments are illustrated in the co- 

 loured plate. 



Form of the leaf. The form of the leaf is recorded by means 



of the "leaf-factor", which is a numerical expression indicating the 



lenght 

 ratio - — --—-. - of the lobe. While every value has been found for 

 breadth 



leaf-factor between 1 (broad lobed) and 5 (narrow lobed\ no plant 



possessing a value between 2 and 3 has been found to breed true 



to that character. All the pure types fall into two distinct groups, 



