SECTIONAL TRANSACTIONS.— D. 433 



The combinations are as follows : 



36 



12 



27MPI 



^^ A^ T [ copigmented malvidin glycoside (bluish mauve). 

 9 Mpl ) 



^ ^^! [ uncopigmented „ „ (reddish „ ). 



3 iVlpl ) 



9 mPI copigmented peonidin glycoside (bluish rose). 



3 mPi uncopigmented „ „ (reddish ,, ). 



3 mpl copigmented pelargonidin glycoside (salmon pink). 



I mpi uncopigmented „ „ (salmon). 



Capt. R. D. Williams. — Chlorophyll deficiencies and flower colour 

 in Red Clover [Trifolium pratense). 



The plant is a diploid and is normally cross-fertilised ; inbreeding has 

 disclosed numerous recessives determining chlorophyll production and 

 flower colour. Nearly half the chlorophyll deficients are lethal in the early 

 seedling stages. Some of the viable mutants are exhibited. The light 

 green types (gb, gc, gd, g£, gh) show a slightly lighter green colour than the 

 normal. Others (gi) are paler, while some (ga, ge) are yellow-green in 

 colour. The colour diflference may be shown throughout the life of the 

 plant or, as in gk, the plant may become progressively greener with age. 

 In other cases, the gene determines a variegated (va, vb), flecked (vc) or 

 speckled (vd) light and dark green mosaic in the leaf. 



The normal purplish red flower colour is determined by at least twelve 

 dominant complementary factors. Seven of the recessive types are shown, 

 viz. pure white (c), white (cy), very faint pink (ca), pale pink (cii), pink (cp), 

 pale mauve (ci), slaty blue (cb). 



Miss U. Philip. — Colours in Drosophila. 



The normal or wild type eye-colour of Drosophila melanogaster is a bright 

 cherry red. Chemical investigation has shown it to be a combination of 

 three water-soluble pigments : a red one which is irreversibly turned into 

 a brown one, and a yellow one which becomes red by oxidation, a process 

 which is reversible. These pigments are deposited during two distinct 

 phases of the pupal stage in pigment cells surrounding the ommatidia 

 proper. 



About fifty different recessive eye-colour characters are known. These 

 can be classed according to the way in which they affect the normal corn- 

 position of the eye-colour, (i) The pigment granules may be present in 

 proportions similar to those in the wild type but fewer in number, as in the 

 series of eye-colours at the sex-linked locus of ' white.' Of the continuous 

 range of types five are selected, namely ' coral,' which is not markedly 

 different from normal, only the transparency being affected ; ^ ' apricot,' 

 ' eosin ' and ' tinged,' which are intermediates ; and finally ' white,' in 

 which no pigment is deposited. (2) In eye-colours of the ' vermilion ' 

 type less brown pigment is present than in the wild type eye. By the 

 transplantation technique it has been established that several different 

 genes represent changes at different stages in eye-colour developinent. 

 (3) In the mutant ' brown ' the red component is missing altogether, giving 

 the aberrant eye a darker and more dilute appearance. In the combination 

 ' scarlet-brown ' no pigment at all is formed, ' scarlet ' cutting out the brown 

 component and ' brown ' the red one. (4) Without affecting the density 

 of the pigmentation the red may be changed to a dark ' sepia ' colour. 



