1909] BROWN—EMBRYO SAC OF HABENARIA 247 
mother cell does not divide the first four nuclei of the embryo sac are 
megaspore nuclei, and of BRown (’08) that the embryo sac of Pepero- 
mia is composed of the descendants of four megaspores, CAMPBELL 
(09) says: “The generally accepted view that in such cases as 
Peperomia and Lilium the embryo sac is a single megaspore formed 
without previous division from the mother cell can hardly be admitted 
to have been disproved by these recent speculations.” In speaking of 
Peperomia, he says that BRown bases his opinion that the first four 
nuclei of the embryo sac represent megaspores upon the fact that cell 
walls are formed in the first two nuclear divisions in Peperomia sintensit 
and cell plates in the same divisions in P. pellucida; while in the third 
division cell plates are wanting. CAMPBELL says that since in the last 
division, which gives rise to sixteen nuclei, cell walls are formed, “this 
seems rather inadequate grounds for assuming that the embryo sac rep- 
resents four spores rather than a single one.” The presence of the cell 
walls was not the only reason for thinking that the embryo sac of 
Peperomia represents four spores; but even if it were, the formation of 
Walls in the last division would offer no difficulty to such a view, for 
walls are usually formed at the last division of the embryo sac of angio- 
sperms and the writer has not been able to find any essential difference 
between the method of their formation in Peperomia and in Habenaria. 
Nor would the reduction of the free divisions in the embryo sac to a 
single one (the third in Peperomia) be a difficulty when we remember 
that the number of these is often large but quite variable in the gymno- 
sperms and has been reduced to two in the ordinary angiosperms. 
The fact remains that unless we assume that the first four nuclei of the 
embryo sac of Peperomia and Lilium are megaspore nuclei, we have 
no explanation for the presence of walls in the first two divisions of the 
‘mbryo sac of Peperomia and for the absence of these walls in the third 
division, or for the presence of cell plates on the spindles of the first 
two divisions of Lilium, features which have been described in no case, 
So far as the writer knows, in which the embryo sac is formed from 
one of four megaspores. we 
CAMPBELL thinks that if the compound nature of the sac of Lilium 
be admitted, we still have to explain the extraordinary departure of 
Peperomia from the usual type, but why two such distantly related 
Plants would be expected to behave alike is not explained. 
