456 BOTANICAL GAZETTE [DECEMBER 
heterotypic division in a cell of the nucellus as the sole criterion for 
determining that this cell is a megaspore mother cell, and that the 
first four resulting nuclei are the nuclei of megaspores. This view 
seems to leave out of consideration the great number of points in the 
life-history of plants at which reduction may take place, and the 
evident tendency among vascular plants toward the reduction of 
sporogenous tissue in the megasporangium and nucellus. 
In the Archegoniatae the archesporial cell may give rise to a large 
mass of tapetum and a considerable number of functional spore 
mother cells. Since we can trace the reduction of these divisions 
until among angiosperms the archesporial cell may without dividing 
form one megaspore mother cell, it does not seem reasonable to sup- 
pose that the divisions of the mother cell to four megaspores may not 
also be left out and the mother cell function directly as a megaspore. 
In this case the heterotypic division might be pushed forward and 
take place in the embryo sac. 
Among the lower plants this reducing division may take place at 
almost any point in the life-history and there seems to be no sufficient 
reason for thinking that it must occur at the same place in all angio 
sperms. 
If the two divisions which form the spores from the mother cell, 
or one of them, have been left out, we could of course expect to find 
no evidence of it other than the entire absence of any signs of the 
division. 
In a recent paper on Cypripedium, Miss Pace (’08) shows that 
the sporogenous cell divides once and one of the resulting cells forms 
the embryo sac, while the other may occasionally divide once. There 
is not even a sign of a cell plate in the first division of the nucleus 
which forms the embryo sac. Miss PAce calls the first two nuclel of 
the embryo sac megaspores, but does not state her reasons for doing 
so. The question might arise as to whether they are megaspores 
or whether one division in spore formation has been left out. That 
the nucleus of the degenerating cell should occasionally divide does 
not seem surprising when we remember the large number of plants » 
which the nucleus of a degenerating megaspore may do so. 
The writer does not wish to be understood as denying that pe 
are two megaspores in the embryo sac of Cypripedium, oF that 
