5 88 
Saxton . — Contributions to the 
scanty cytoplasm of the cell. At a slightly later stage a single functional 
megaspore is found (Fig. 37 ) lying just below two deeply staining and 
abortive nuclei. These three have evidently been derived from the mother- 
cell. The microphotograph (Fig. do) shows one of the two sections from 
which Fig. 37 was drawn. The second abortive nucleus appears in the next 
section. It will be noticed that the megaspore nuclei are much smaller 
than those of the surrounding tapetal cells. No stages between Figs. 36 
and 37 were secured ; they would not be likely to show any marked diver- 
gences from the sequence of megasporogenesis as described by Noren (37) 
and Nichols (36) for Juniper us, by Knischewsky (23) for Thuja , by Coker (9) 
for Taxodium , and by Miyake (32) for Cunninghamia . Lawson (26 and 27) 
seems to have obtained only scattered stages in Cryptomeria and Libocedrus , 
and it is not clear in either case from his figures that the cells named mega- 
spores are really such. It seems just as likely that they may represent 
a group of megaspore mother-cells similar to that figured in other 
Cupressoi’deae. 
If Lawson’s explanation of his figures is correct, it is clear that Crypto- 
meria and Libocedrus differ widely from all other investigated Cupressoi'deae 
in this respect ; since, however, the figures as published would bear another 
interpretation, namely, that the earlier stage was archesporium and the later 
one a group of megaspore mother-cells precisely similar to that found in 
the other genera, which agree very closely with one another, one is tempted 
to believe that Lawson has fallen into the error of mistaking mother-cells 
for spores. A re-examination of Libocedrus and Cryptomeria is certainly 
desirable in order to settle this point. 
The free nuclear divisions in the young prothallus are at first simul- 
taneous (Fig. 38 shows one of the thirty-two dividing nuclei met with at 
the sixth mitosis), but whether these strictly simultaneous divisions occur 
later has not been determined. 
Late stages of the hollow embryo-sac, shortly before the commence- 
ment of cell-formation, reveal an important difference between Tetraclinis 
and the Callitroideae ; in the latter the prothallus is narrow and pointed at 
the apex, and the pollen-tube more or less overlaps its tip some time 
before cell-formation begins ; in Tetraclinis, on the other hand, the apex of 
the young prothallus is quite truncate, just as in Thuja (Land (24)) and 
other Cupressoi'deae, while the pollen-tube has not penetrated more than 
half-way from the apex of the nucellus to the apex of the prothallus. 
A number of preparations have been obtained showing the formation 
of alveoli in various stages and the subsequent formation of closed cells. 
The first alveoli are seen growing in from the sides of the prothallus, while 
scarcely any trace of them can be seen growing down from the truncate apex 
(PL XLVI, Fig. 61 ). From a comparison with later stages it seems fairly 
certain that the alveoli, usually about nine or ten in number, destined to form 
