278 BOTANICAL GAZETTE [APRIL 
and states that the nuclei of the male and female plants were in all 
cases apparently identical, both in the number and in the character 
of their chromosomes. More complete studies have been made 
by Dariinc (5) in Acer Negundo, and by StTRASBURGER (38) 
in Melandrium rubrum, Cannabis sativa, Mercurialis dioica, and 
_ Bryonia dioica. Both writers report that in the reduction division 
of the microspore mother cells they find no evidence of anything 
which might be considered a “‘sex determinant.’’ Negative results 
in these few cases, of course, do not prove that a sex determinant 
never occurs in plants, for it will be remembered that such a con- 
dition has been demonstrated in only a comparatively few animals. 
Dimorphic heterostylous plants present, as will be pointed out 
below, such striking resemblances to dioecious plants that the 
present study was undertaken in the hope of finding, in the reduction 
‘division of the microspore mother cells, some indication of a mor- 
phological difference in the chromosomes which go to make up the 
nuclei of the microspores. 
Material of several species was prepared, but only two, Fago- 
pyrum esculentum and Houstonia caerulea, proved favorable for 
study. The material used was all collected in the spring and 
summer of 1910. The buds of Fagopyrum were taken from vig- 
orous plants under cultivation; those of Houstonia were nearly 
all from an old, well-established lawn, where many of the clumps 
had very likely persisted for several years. 
The writer wishes to acknowledge his indebtedness to Professor 
A. W. Evans, at whose suggestion this study was undertaken, for 
assistance in all parts of the work, and to Dr. G. E. Nicuots for 
generous aid in the collection and preparation of material. 
Historical sketch 
PERSOON, in 1794, notes that in certain species of Primula 
there are two forms which exist in about equal numbers and differ 
from each other in the length of their pistils and stamens. This 
is, according to Von Mout (p. 326), the first description of the 
condition now known as heterostyly. 
This condition was apparently regarded as a mere variation in 
form until the time of DARwIn, who discusses several dimorphic 
