1912] STEVENS—HETEROSTYLOUS PLANTS 295 
and two in the middle; while in the long form the arrangement 
shows seven in the periphery and one in the middle. This arrange- 
ment may of course be accidental or it may be mechanical, due to 
the difference in the chromosomes*(compare figs. 14 and 15 with 
figs. 16 and 17). 
A careful examination of the cells in the late anaphase of the 
heterotypic division of the short-styled form failed to show any 
difference in the chromosomes (figs. 14 and 15). In the long-styled 
orm, however, the “‘central’’ chromosome is apparently consider- 
ably larger in one of the daughter nuclei of the heterotypic mitosis 
than is its synaptic mate in the sister nucleus (figs. 16 and 17). 
While this condition is apparently constant, little importance can 
be attached to it until more is known of the inheritance of hete- 
rostyly in the buckwheat,? and of the reduction division of the 
megaspores. It bears a striking resemblance, however, to the con- 
dition found in the sperm mother cells of Lygaeus and other insects 
(WILSON, 40, p. 59) in which there is an “x”? chromosome which 
has as a synaptic mate a smaller ‘“‘y”’ chromosome. 
GROWTH OF THE POLLEN MOTHER CELLS 
The difference in the size of the pollen grains of the two foenis 
has been referred to above. As a corresponding difference in size 
was apparent in the pollen mother cells during early stages, an 
examination was made to determine whether a similar difference 
in size occurs in the somatic cells. Buckwheat seeds were allowed 
to germinate on moist filter paper, and when the roots were about 
half an inch in length the tips were removed with a sharp razor 
and fixed at once. Seeds and root tips were carefully marked to 
correspond and the seeds planted. 
The seedlings developed readily, and when the plants blossomed, 
microtome sections of the root tips were prepared and the size of the 
embryonic cells of the two forms compared. The cells measured, 
of course, were always in the same stage, usually the metaphase. 
Some variation in the size of the embryonic cells even in the same 
Stage was noted, but no constant difference between the two forms 
Serrano s experiinents ¢ on ~ — as he himself states, were very imperfect, 
and gav f either form produced plants of both forms. 
