Life-history of Tetroclinis articulata. 
593 
Fertilization and Development of the Proembryo. 
As in other Cupressoideae, it is customary for both the male cells to 
be functional, passing into and fertilizing two adjacent archegonia. One 
case has been seen, however, where all four nuclei were discharged from the 
pollen-tube into a single archegonium ; a very similar case is figured by 
Knischewsky (23, Fig. 45) in Thuja . 
Post-fertilization stages are readily recognized by the starch sheath 
which invariably surrounds the fusing nuclei. Although no very conclusive 
evidence of the origin of the sheath was obtained in the present case, there 
can be little doubt that it is simply the cytoplasm of the male cell. It is 
curious, however, that starch is not noticeable in the mature, or nearly 
mature, male cell, while it is always a conspicuous feature of the sheath. 
The same peculiarity was remarked by Strasburger (53) in Juniperus , but 
Nichols (36) succeeded in demonstrating the starch in the male cells of this 
genus, and it has also been seen by Coker (9) in Taxodium ; it seems, 
therefore, very probable that starch is commonly present in the cytoplasm 
of the male cells, but in rather an obscure form in some cases, becoming 
much more conspicuous after fertilization. 
Fig. 47 shows the conjugation of the male and female nuclei. This 
case is typical of four out of five similar stages seen. The male nucleus is 
considerably smaller than the female, and in the latter the nuclear contents 
are somewhat more scanty than in the former. A large reticulate nucleolus 
is seen in the female nucleus. Fig. 48 shows an exceptional case where the 
male nucleus is below the female. It is quite clear, both from the structure 
and the relative size, that the lower nucleus is the male, and it may be 
mentioned that the actual difference in size is greater than is apparent from 
the section, since the female nucleus extends considerably further than the 
male in the sections both above and below that figured. I should doubt 
whether the volume of the male nucleus is ever more than one-third of that 
of the female. Fig. 49 shows one of two cases seen where fusion is quite 
complete, no trace whatever remaining of the line of junction of the two 
nuclei. The structure, however, is simply that of a resting nucleus, so that 
here fusion is entirely complete before any preparations are made for the 
first sporophyte division. In Pinus (Blackman (4), Chamberlain (6), Fer- 
guson (17)) preparation is made for this division by both nuclei before the 
membrane between them breaks down, and no mingling of the nuclear 
contents takes place until after chromosomes are organized, and although 
no other genus has been investigated so completely, it appears probable 
that the same is true for other Pinaceae. The records for other families are 
so scanty that it is not possible to generalize ; in Juniperus , however, both 
Noren (37) and Nichols (36) record complete fusion of the two nuclei in the 
resting stage. 
