96 LOCK : PRESENT STATE OF 



completely masked* or hidden when the indent is present, but 

 the wrinkled character is not. Thus, an indent plant which is 

 a heterozygote in respect of the pair round-^vl'inkled will bear 

 a mixture of indent and wrinkled seeds in the proportion of 

 three to one. 



It seems that the indented character only makes its appear- 

 ance in association with a pigmented testa. f So that when a 

 pigmented indent plant is crossed with a non-pigmented plant 

 having round seeds, all the non-pigmented jjlants in F 2 have 

 again round seeds. The indent character is thus itself masked 

 in the absence of pigment, and may make its appearance as a 

 reversion when a rourd-seeded pigmented plant is crossed with 

 a round-seeded unpigmented, as was observed both by Tscher- 

 mak and the present writer. In this case the non-pigmented 

 parent must have borne the indent allelomorph in the masked 

 condition. 



We have seen that the indent character — a character which 

 affects the cotyledons of the embryo — segregates by plants. 

 It is therefore a maternal character, which becomes impressed 

 upon the offspring in some way unconnected with heredity. 

 This result may be contrasted with the effect of the pheno- 

 menon known as xenia — also described in peas — in which the 

 character of a hybrid embryo directly affects the maternal 

 tissues. Phenomena not unlike that shown by the dimpled pea 

 character have been described in wheat and in maize (25, 27). 



(iii.) Besides roundness and wrinkledness and the presence 

 and absence of the indent character, other slight nuances of 

 shape are to be observed in different varieties of peas. These 

 are often quite characteristic, though almost impossible to 



* A masked character is a dominant allelomorph which remains 

 invisible (formerly described as latent or, incorrectly, as recessive). This 

 invisibility depends upon the presence (or absence) of an allelomorph 

 belonging to a totally distinct pair. 



Thus, in the case of many colour characters, the appearance of the 

 colom- depends upon the simultaneous presence of two dominant 

 allelomorphs A and B. ABAB is coloured and so is any other zygote 

 containing both A and B, such as ABab; but AbAb, aBaB, abab, &c., 

 are all colourless. In this case both A and B are masked respectively — 

 each in the absence of the other. 



t There is evidence that it may sometimes be coupled with a parti- 

 cular type of testa colour. (Tschermak, 19.) 



