246 EFFECTS OF EXPOSING GERM-CELLS TO RAYS OF RADIUM 



In his paper on infertile hybrids, Wilson ^'^ describes a zonal 

 pelargonium-hybrid of interest in this connection. In making a 

 cross between two variegated zonal pelargoniums, the variegation of 

 the seed-parent, he says, was of the usual kind, "the peripheral 

 zone of white enclosing a green center and sending into it pro- 

 jections of more or less intense variegation. In the pollen parent 

 the variegation, also white, occupied the center and margin of 

 the leaves. . . . The seedlings resulting from the cross were in 

 the majority of cases non-variegated and coarse. A few were 

 variegated from the first, but only one has been made special note 

 of. Its cotyledons were blotched with white, etc. . . . Very 

 soon three distinct vegetative regions were differentiated in the 

 seedling under discussion ; one including leaves with normal chlor- 

 ophyll development, the next with variegated leaves, and the third 

 with leaves quite destitute of chlorophyll. If a leaf arose in a plane 

 between any two regions it embodied in itself features of both. . . . 

 Ultimately a branch lying wholly in each region was produced. 

 Variegation was only once seen in the green branch, a small patch 

 of white occurring in one leaf. The variegation of the variegated 

 branch was identical with that of the seed-parent. The albino 

 portion showed marked persistence. . . . No trace of green was seen 

 in the branches."* 



Here we have recorded the case of a known hybrid in which 

 the characters entering into combination expressed themselves in 

 such a way that only one set of characters appeared on one side of 

 the plant, the other set on another side, while the organs in an 

 intermediate position partook, in bilateral fashion, of both sets of 

 characters. 



It is in view of the above facts and considerations that I believe 

 that the morphologically asymmetrical evening-primrose is funda- 

 mentally a hybrid, and that its asymmetry may be due to a segre- 

 gation, in opposite sides of the plant, of the characters brought 

 together in the cryptomeric crossing. 



One other possible explanation of this plant must not be over- 

 looked, and that is an interpretation of it as a bud-sport in which 

 only one half of the bud was affected. In this particular instance, 

 and on this theory, the sectorial variation may be an expression of a 

 change from dominancy to latency of some of the specific biennis- 



*The white portion was regarded as a parasite on the green portion. 



