W. Bateson and a. E. Gatrdner 273 



Attempts to use the male-steriles as males in crossing have hitherto 

 failed, the pollen produced by them being very small in amount. 



Much interest would attach to the genetics of plants made in such a 

 way that the male-sterility was brought from the maternal side into 

 combination with one or other of the hermaphrodite factors introduced 

 from the paternal side. Various possibilities are thus opened up. On 

 these questions we have as yet no suflScient evidence, Expt. 19 being 

 the only one bearing on the point. There the hermaphrodite element 

 was that of the female side of procumbent, and it was brought in from 

 the male side of a plant homozygous in F3 or a homozygous F2. Tried 

 on a male-sterile it gave 6 male-steriles and 1 9 . That it should have 

 given the 9 is worth noting, but work on a large scale is required to 

 explore the many alternative distributions which will possibly be 

 encountered. Material for these investigations is being prepared. 



Plants in which the distribution of factors differs on the two sexual 

 sides of the same plant now form such a prominent subject of genetical 

 consideration that some simple terms are required to facilitate discussion. 

 We suggest that in the ordinary Mendelian distribution the segregation 

 might be called amhilateral, effected on both sexual sides of the plant 

 as distinguished from the unilateral segregation which carries the 

 allelomorph wholly to one sexual side'. 



In other examples, e.g. the double-throwing single in Matthiola, we 



might speak of the segregation as partially unilateral. The exception 



mentioned above (Expt. 11) may indicate that here also the unilaterality 



may on occasion be partial, but unless the phenomenon recurs its 



significance is doubtful. 



Details of Experiments. 



P = Procumbent. il/S = Male-sterile. 



The "tall" strain is that first raised here by selection-; "Dark blue" is another 

 raised since ; "Dark blue tall" is another, now pure, raised by combination of the above. 



Total ... 716 — 



5. MS X P 



5 mothers X 3 fathers gave ... ... 101 2 



The 2 MS resulting were doubtless due 

 to self-fertilisation 



1 Proc. Ro7j. Soc. 1920. - Journal of Genetics, Vol. v. 1916, p. 199. 



