286 BOTANICAL GAZETTE - [APRIL 
doubtless receives pollen from several flowers, among which it 
could easily ‘“‘select” the favorable pollen, by inducing a more 
rapid growth of the pollen tube of the “legitimate” kind, exactly 
the method by which illegitimate fertilization is prevented, under 
normal conditions, in heterostylous plants. 
The morphological differences shown by the different forms of 
heterostylous plants are really very slight compared with their 
' physiological differences. According to the view suggested above, 
dimorphism, trimorphism, and dioeciousness would be merely 
morphological expressions of physiological differences common to 
many plants. Such an hypothesis would account for the origin of 
dioeciousness and heterostyly at different points, widely separated 
both geographically and genetically throughout the plant kingdom. 
Fagopyrum esculentum 
The dimorphous flowers of the buckwheat were first described 
and very accurately figured by HERMANN MULLER (28, p. 165; 
also 29, p. 509). As MULLER points out, there are ‘‘in each form 
8 stamens, 3 closely surrounding the styles and opening outwards, 
the 5 others inserted more outwards and opening inwards.”” The 
place occupied in one of the forms by the anthers is occupied in the 
other by the stigmas, a perfect adaptation for cross pollination by 
the numerous insects which visit the flowers for the sake of the 
honey secreted by the 8 globular nectaries at the base of the fila- 
ments. There is apparently no difference in the structure of the 
stigmas in the two forms, but the pollen grains of the short-styled 
form are larger than those of the long-styled form, their diameters 
being in about the ratio 5:4. There appear to be no secondary 
differences in the vegetative structure of the plants. 
The flowers are as arule true to form, and there is no difficulty 
in distinguishing long-styled from short-styled plants. Occasional 
flowers with the stigmas at the anther level, however, are seen on 
normal long-styled plants. Seldom more than one such flower 
occurs on a plant and this is usually the first which opens. A similar 
condition has been noted by BATESON and GREGORY in Primula 
(2, p. 583). One plant, however, was noted among some grown 
