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On the Inheritance of Certain Invisible Characters in Peas. 

 By E. H. Lock, M.A., Fellow of Gonville and Caius College, Cambridge. 



(Communicated by W. Bateson, F.K.S. Eeceived October 1, — Eead November 22,. 



1906.) 



In a paper which appeared recently in the ' Proceedings of the Eoyal 

 Society,' Messrs. Bateson and Pnnnett and Miss Saunders showed that the 

 visible appearance of certain characters in Sweet Peas and in Stocks was 

 due to the association together in the same zygote of factors belonging to 

 independent but complementary allelomorphic pairs. If both the com- 

 plementary factors were not simultaneously present, no hint of the presence- 

 of the characters in question was to be detected without breeding tests \ 

 nevertheless, the presence and absence respectively of such a factor constitute- 

 a pair of allelomorphs, and segregate in complete accordance with Mendel's 

 law. 



The present communication deals with a similar but somewhat simpler 

 phenomenon exhibited by certain colour characters of the testa of the 

 ordinary field or garden pea — the species to different cultivated varieties of 

 which the names Pisum sativum and P. arvense have been given. The case 

 is simplified by the fact that here only one of the two complementary factors, 

 is by itself invisible. The presence of the second factor is invariably 

 accompanied by the appearance of a definite visible character, whether the 

 invisible factor is present or not. The present examples of " latency " are of 

 special interest on account of the classical nature of the material, as well as- 

 because it has been suggested that Mendel was in error in his own account 

 of the characters of the testa in peas. It may be stated at once that this is 

 not the case. Mendel's account is perfectly correct so far as it goes. The- 

 grey colour of the testa, constantly associated with coloured flowers and 

 coloured axils, is a simple Mendelian dominant to colourless testas coupled 

 with white flowers and green axils. 



The testa may, however, show other colours in addition to the well-known 

 grey. In Ceylon, in 1902, the writer found in cultivation a pea, the appear- 

 ance of which strongly suggested that it came very near to the primitive 

 ancestor of cultivated peas. We are concerned here only with the characters 

 of the testa. This showed an essentially grey ground colour (greenish or 

 yellowish), and, in addition, two distinct sorts of coloured markings : — 

 (1) small specks of a very deep purple colour, the presence of which may be 

 briefly denoted by the letter p. ; and (2) a mottling or marbling of brown„ 



