TJie Inheritance of Flower Colour in Antirrhinum majus. 289 



The colours of all these types are sap-colours, not plastid-colours. 



Forms of the crimson and magenta types occur in which the tube is ivory, 

 while the lips are magenta or crimson respectively (figs. 7 and 6). The term 

 "delila" was used by Professor De Vries* for such forms and has been 

 adopted in this paper. 



Yellow and magenta colours are produced by the corresponding sap-colours 

 in the cells. Crimson colour in the lips is due to the simultaneous presence 

 of magenta and yellow saps in the cells. That such is the case is easily seen 

 in a microscopical examination of the tissue of the lips of a crimson flower. 

 Groups of cells containing pure yellow or pure magenta saps are found among 

 crimson cells in which the colour is undoubtedly due to a mixture. 



With the exception of the albino type, the flowers of all types used have, 

 irrespective of the colour of lips and tube, a constant orange-yellow palate ; 

 smaller patches similar in colour generally appear at the base of the tube on 

 either side. This summer Mr. Bateson has shown me white types, some of 

 which had a little orange-yellow colour on the palate, while others had in 

 addition the yellow patches on the tube. Matings will be made with these 

 types, but all whites employed and described in the experimental work have 

 been entirely without colour. 



The inheritance of the corolla colours can be represented by the following 

 factors, which have been found to follow the Mendelian inheritance : — 



Y. — A factor representing yellowf colour in the lips associated with ivory 



tube-colour. 

 I. — A factor representing ivory colour in the lips. 

 L. — „ magenta „ „ 



T. — „ „ „ in the tube. 



Small letters, y, i, etc., denote the absence of these factors. 

 From experimental evidence it appears that : — 



1. All zygotes, from which Y is absent, are white, though they may 



contain any of the factors I, L, and T. 



2. The factor T is not manifested unless L is also present in the zygote ; 



that is, no magenta colour appears in the tube unless magenta colour 

 be also present in the lips. 



3. All zygotes containing Y are coloured. The actual colour may be 



modified and determined by the presence of one or more of the 

 remaining factors. A zygote containing Y only or Y and T is yellow. 



* < Mutationstheorie,' Lief. IV, pp. 194—206. 



t This, of course, does not refer to palate colour, which may be regarded as a separate 

 character. 



