1903] GAMETOPHYTES AND EMBRYO OF TAXODIUM 15 
lination the inner cells near the tip begin to grow in at certain 
points, and approaching the center almost completely close the 
micropylar cavity (4g. 37). There soon begins to appear in 
the tip of the integument an irregular ring of lignified cells with 
thick and pitted walls, which serves to strengthen this exposed 
end (fig. 49). 
THE MEGASPORE. 
The megaspore mother-cell cannot be distinguished from its 
neighbors until shortly before pollination. It is the basal or 
next to the basal cell of one of the distinct cell-rows which are 
evident in the center of the nucellus, and is situated at the same 
level as the point of insertion of the integument (figs. 35, 37)- 
In this respect Taxodium agrees with the Cupresseae and differs 
markedly from Sequoia (Shaw, ’96). At the time of pollina- 
tion the megaspore mother-cell is slightly larger than the cells 
immediately surrounding it. Only a single megaspore mother- 
cell is present at this stage, but one case was found (fig. 50) 
in which the nucellus contained two young prothallia, one of 
which was larger than the other. Whether these were derived 
from two mother-cells or from the same mother-cell is a matter 
of conjecture. In this respect also Taxodium is seen to differ 
from Sequoia, in which Shaw (96) and Arnoldi (’99”) have 
found it the rule for a number of prothallia to be developed. 
Hofmeister (751) mentions the occasional presence of two pro- 
thallia in Pinus silvestris and T. axus baccata (confirmed since by 
Farmer [’92] for Pinus and by Jager for Taxus), and I have 
found two in Podocarpus and Zaxus baccata canadensis. With 
these exceptions the development of more than one prothallium 
‘has not been observed in the conifers. 
The mother-cell increases slowly in size after pollination, and 
in about ten days the first division occurs. /ig. 39 is a mother- 
cell shortly before its first division. It is abundantly supplied 
with starch grains, as are also the adjoining cells for about one 
layer. It will be seen that the nucleus is in synapsis, the mesh- 
Work being in a contracted mass near the nucleolus. Such a 
ma Napsis is found by Juel (’00) at the same stage in Larix sibt- 
7ica. He also mentions the presence of denser fibrous areas at 
