34 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



A LECTUEE ON THE HEEEDITAEY OHAEAOTEES IN 



THE POTATO. 



By De. Eedcliffe Salaman. 



[Read April 30, 1912; Mr. A. W. Sutton, F.L.S., V.M.H., in the Chair.] 



This year begins my sixth season of work on the potato, and although 

 the results are still far from complete and in 'some instances equivocal, 

 yet it may not be out of place to record their progress for the benefit 

 of fellow- workers. 



I am the more encouraged to take this course because I am con- 

 vinced that in the application of the Mendelian principles of research 

 to the potato, one has already obtained sure evidence of practical 

 economic benefits. 



In this lecture it is not necessary for me to enter into the principles 

 on which Mendelian research is conducted, but it will suf&ce to say 

 that my entire efforts have been directed towards the analysis of the 

 factors which underlie and determine the varying characteristics of 

 the potato plant. This analysis has not been conducted primarily 

 with an economic outlook, but rather as an attempt to isolate the 

 several characters, great or small, whether in flower, haulm, or tuber, 

 in the same spirit in which a chemist would analyse some complex 

 body. The result has justified the method, for it has, as it were, 

 illustrated the old adage — ■ 



Look after the pence, and the pounds will look after themselves; 



for whilst studying certain characters which appeared purely of 

 academic interest, I have, I think, been fortunate enough to light on 

 facts which may later have an important economic bearing. 



I propose to give a simple account of the characters thus far 

 isolated in the potato plant, and to leave a fuller and detailed descrip- 

 tion for a later publication. 



The Flower. — The colour of the flower of the potato may be either 

 white, heliotrope, or purple, the last of diverse shades. 



A chromogen body, a reddening factor, and a purple factor have 

 been recognized. The heliotropes are due to the reddening and 

 chromogen factor being united in one individual, and the purple 

 flowers are due to the further addition of the purpling factor. White 

 flowers are due to the absence of one or more of these deter- 

 miners. In addition the potato flower is peculiar inasmuch as the 

 pigment is confined to one or other of the surfaces of the flower. 

 In all the domestic varieties and their descendants which I have 

 handled, the colour is limited to the upper surface and is inhibited on 

 the lower; on the other hand, in Solanum 'ehiherosum one finds the 

 pigment on the lower surface and an inhibitor to pigment present on 



