No. 636] 



15 



ently releii-ated to tlic innlc >\(\v of the plant, wliile the- 

 female side tako the lici-tnapliroditt' ra<'t(>r. Segrega- 

 tion in re.uai'd to the -aiiic rccc^-iNc may take place in 

 one of two ways. It may he iiHildfcrdl, as it is when in 

 heterozygous association with the female of the tall 

 flaxes, or it may be amhilateral and unrestricted to 

 either sex when it is in association with the female of 

 the oil flax. We must infer that the female halves of 

 the two types differ in some critical respect which decides 

 the manner of the segregation. 



Unilaterality may also show itself as a difference in 

 the closeness of linkage on the two sex-sides of the same 

 plant, and no doubt this fact may have a bearing on the 

 interpretation of the foregoing cases. The late K. P. 

 Gregory discovered the first case of this, in Primula 

 sineMsis. He found that the linkage between magenta 

 color and short style was- closer in the eggs than in the 

 pollen. Eecent work on a larger scale has given 10.9: 1 

 as the female linkage and 6.4 : 1 for the pollen. A sim- 

 ilar difference has been also found for the linkage be- 

 tween green stigma and "reddish" stem (as opposed 

 to dark red), the value being 29.8:1 for the eggs and 

 41.7:1 for the pollen. In both examjtU's, individual 

 families show wide fluctuations, and tliex.' vahies >lioiihl 

 for the present be regarded as approximate only. What- 

 ever be their meaning, they show tliat some segregation 

 has occurred in the t'oimation of the two sets of sexual 

 organs, such that the |)rocess of uametic differentiation 

 is not the same in both. 



Besides these examples of differentiation Ijetween the 

 male and female sides, there are others proving that 

 segregation may occur at other stages in somatic devel- 

 opment. The most obvious examph's ar(^ the variegated 

 plants. I have discussed this suhjcct el-ewhei-e in con- 

 nection with reversible periclinni '•diima ra-" of wiiite 

 over green which produce shoots having the white in- 

 ch )se<l with tlie green.^*' To these must now be added 

 the ca^es in which the plants arising from adventitious 



10 Jour. Gen., Vol. 7, p. 93 (1919). 



