84 CoMPARATIVE EMBRYOLOGY OF THE RUBIACEAE 
The first division in these plants is therefore heterotypic, in the 
sense of Flemming and Strasburger, and the second is homotypic, 
and results merely in the separation of the granddaughter rods al- 
ready formed. The individuality of these bodies is, however, lost, 
so far as can be seen, in the resting nucleus preparatory to the 
second mitosis by fusion of the rods and by more or less com- 
plete diffusion of the chromatin. 
It is concluded from this evidence that the divisions described 
are true tetrad divisions, and the four resultant cells as spores. It 
has on several occasions been urged that the position of these cells 
in the nucellus of angiosperms speaks against this interpretation, 
but it is not surprising that such an arrangement should occur in 
the ovule when we remember that the position of the spindle and 
through the spindle often of the cell wall is determined by growth, 
and that the growth of the sporogenous tissues is conditioned by 
a very different sort of environment from that found in the sporan- 
gium of the pteridophyta. 
But the evidence is fast accumulating to slıow that. it really 
frequently happens that the divisions are not such as to produce a 
single row of cells. This evidence has recently been collated by 
Max Koernicke * to which may be added the cases recorded by 
G. M. Holferty t as occurring in Potamogeton. 
Adding to the above the facts derived from a cytological study 
of the divisions themselves, I fail to see the cogency of the state- 
ment made by Atkinson f that the embryo-sac of the angiosperms 
“arises directly from the nucellar (sporangial) tissues or from the 
archesporium, without the intervention of spores." That the 
spores in many forms are losing or have already lost their physio- 
logical identity as spores is indeed true, but it is certainly a most 
remarkable fact that cannot be brushed aside that in the most ex- 
treme cases Lilium for example, the process of giving rise to these, 
cells is identical in all essential respects, to the process in all other 
plants, both pteridophyta and spermatophyta, in which this point 
has received careful study. 
* Studien an Embryo sac Mutterzellen. Er) 
T Ovule and Embryo of Potamogeton natans. t. Gaz. 13: 339. ۰ 
: 1 s ie Homologies and probable Origin of the Embryo-sac. Science, 1. 13: 
