Saxton.—Contributions to the Life-History of Caliitris. 561 
distinct, and, in addition, a large nucleus of quite a different character is 
present. This must represent some abnormal structure. 
6. Fertilization and Embryogeny. Only one preparation has been 
obtained which undoubtedly shows the sexual nuclei in contact in two 
adjacent archegonia. (These are the lowest but one, and the lowest but 
two of the group of archegonia in Fig. 12.) One of these is shown in 
detail in Fig. 17. The structure of the two nuclei is exactly identical, each 
containing a large reticulate nucleolus. This figure closely resembles 
Lawson’s ( 7 ) fig. 29 of Thuja , but in the present case a number of plasmic 
fibres may be seen radiating from the outside of both nuclei. These are a 
conspicuous feature in both the fertilized archegonia, although nothing of 
the kind has been described in similar stages of other Conifers. The 
male nucleus is also relatively larger here than in Lawson’s figure cited 
above. 
The cytoplasm is denser and more homogeneous towards the apex of 
the archegonium, probably due to the presence of the cytoplasm of the 
male cell. No starch can be seen in the archegonium. A comparison of 
Figures 13 (archegonium), 1 6 (male cells), and 17 1 (fertilization) will show 
that the size of male and female nuclei before fertilization is almost precisely 
identical, but the male nucleus seems to become a little smaller inside the 
archegonium. 
Early stages of the proembryo are wanting. The mature proembryo, 
like that of Widdringtonia , completely fills the archegonium. The arrange¬ 
ment of the cells shows considerable variation. Two mature proembryos 
are shown in Fig. 18 in median longitudinal section, and another in tangen¬ 
tial section in Fig. 19. More than eight cells are present in a mature 
proembryo. 
A dividing nucleus from a mature proembryo is drawn in Fig. 20 (not 
all chromosomes shown). The large spindle and short chromosomes are in 
striking contrast to the much shorter spindle and long chromosomes of the 
divisions in the prothallus cells (Fig. 21, not all chromosomes shown). The 
latter are frequent at this time, giving rise to the typical bi- and multi- 
nucleate cells of the mature prothallus. In a former paper ( 13 ) the opinion 
was expressed that the number of chromosomes in gametophyte and sporo- 
phyte respectively were in the neighbourhood of 12 and 24. I am now 
convinced that the numbers are somewhat less than that, the thickness of 
the chromosomes tending to make the number appear more than is actually 
the case, and the estimation difficult. For the same reason it is impossible 
to represent more than a few of the chromosomes in a drawing: The 
numbers are probably nearer 10 and 20 or perhaps 8 and 16. 
In the same paper ( 13 ) a comparison was provisionally suggested 
between the multinucleate prothallus cells of Widdringtonia and Caliitris 
1 Figure 13 is drawn on a considerably larger scale than 16 and 17. 
