PRELIMINARY NOTE ON HETEROSTYLISM 

 IN OX ALLS AND LYTIIRUM. 



By N. barlow. 



The following paper deals with the heredity of the three forms in 

 trimorphic heterostyled plants. The work is fxr from complete, bnt 

 is perhaps worth publishing as the numbers obtained are large, and 

 certain definite conclusions have already been reached. No factorial 

 interpretation of the results, however, has at present been devi.sed. 



Both Darwin (1) and Hildebrand (2) worked at the descent of the 

 three forms in trimorphic species, but in Darwin's case only as a side 

 issue. Moreover their numbers are not in agreement, and, with the 

 exception of Darwin's self-fertilized Lythrums, the results are no great 

 help to us at present. 



Bateson and Gregory (3) have shown that dimorphism in Primula 

 is a case of simple Mendelian inheritance. The long-styled plants 

 are always recessives (RR), whereas the short-styled plants are either 

 homozygous for the dominant short style (BD), or heterozygous, con- 

 taining both D and R. The unions therefore between long- and 

 short-styled plants can be of two kinds ; the F^ will either consist 

 of short-styled plants only, or there will be equality of longs and 

 shorts. 



In dealing with trimorphism, there is apparently a much greater 

 degree of complexity than might be expected in the light of these 

 simple results obtained for dimorphic species. 



The three forms within each trimorphic species only differ from 

 one another in the developement of their sexual organs, and in the 

 size and sometimes in the colour of the male sexual cells themselves. 

 Each individual has two distinct sets of male organs, and one female 

 oi-gan, arranged in three tiers. Thus each of the females of the 

 three different types can be pollinated by six perfectly distinct males, 



