138 BOTANICAL GAZETTE [avcust 
number of flowers were pollinated early in January. Three weeks 
later the ovaries had swollen to the size of large peas, and the 
gardener—a veteran in the growing of the Richardia—was con- 
fident that seed would be set. Within the following week most 
of these had begun to wilt, but a very few continued to grow until 
they were as large as small hazel nuts. Within two weeks almost - 
all were withering, and from then on the molds rapidly made away 
with them. Five per cent or less 
of the pollinated plants produced 
seed. 
The explanation of this be- 
havior is to be found in the fact 
that the greater number of ovules 
are congenitally sterile and 
develop no embryo sac. In some 
cases no cell can be discovered 
that can be definitely identified 
as a primary archesporial cell. 
In other cases it would seem that 
a potential archesporial cell makes 
its appearance, but fails to com- 
plete its normal course of develop- 
ment. The latter is to be inferred 
from the fact that the number of 
primary archesporial cells 
Fic. 40.—Richordia africana: disin. encountered in the very young 
tegrating sterile nucellus and tip of | ™aterial vastly exceeds the num- 
ipl a ber of embryo sacs in the more 
mature material. 
Sections of pollinated pistils containing sterile ovules demon- 
strated the fact that, in some cases at least, the pollen tube pene- 
trates a sterile ovule, and reaches the tip of the nucellus. The 
fact that the pollinated sterile ovaries reach a considerably higher 

stage of development before withering than do unpollinated ovaries 
of the same sort would appear to be due to the stimulus of pollina- 
Hon. At all events, the writer can find no other cause to which 
it can reasonably be attributed. The direction of the pollen tube 
an Oe ee ee 
