13 
Embryo of Sequoia sempervirens. 
showed the daughter-nuclei well organized, with the kinoplasmic fibrils 
stretching between them. As near as could be estimated, the number of 
chromosomes appeared to be sixteen. These various stages of the dividing 
nuclei had an influence upon the rate at which the cell-plates were formed, 
and consequently the various regions of the prothallium showed all stages 
in the development of the plates. 
While the daughter-nuclei resulting from this division are being 
organized, the continuous fibrils of the spindle persist and increase in 
number ; the result is that each daughter-nucleus is surrounded by a system 
of kinoplasmic radiations. These radiating fibrils not only join the sister- 
nuclei but they connect with the fibrils radiating from the other neighbouring 
nuclei. The result is that certain regions of the prothallium show large 
numbers of nuclei all joined together by systems of radiating fibrils, as 
shown in Fig. 15. Each nucleus at this time is enveloped in a dense 
granular zone of cytoplasm, from which the system of kinoplasmic fibrils 
radiates. The radiations show all the characters of ordinary spindle- 
fibrils, and they apparently have the same origin, that is, they are differ- 
entiated out of the cytoplasm. The first indication of the plate appears in 
the form of small granules or thickenings on the fibrils. These thickenings 
occur about midway between the nuclei, and as they increase in size the 
fibrils become less numerous in the vicinity of the nuclei. This would 
suggest that the fibrils were transformed into plate-forming substance, in 
much the same way as Timberlake (1899) has indicated. As illustrated 
in Fig. 1 6, the thickenings occur on all the fibrils stretching between the 
nuclei, so that each nucleus becomes completely boxed in by the developing 
plates. Different regions of the prothallium showed various stages in the 
formation of the plates. In a single section we may have conditions 
represented in Fig. 15 and Fig. 16, or where the daughter-nuclei are just 
being organized. 
In the upper portion of the prothallium some of the cells may be very 
large and elongated. These are no doubt the structures which Arnoldi 
(1901) has described as ‘Alveolen.’ I find, however, that the archegonial 
initials may develop much below this region, and I therefore cannot endorse 
Arnoldi’s view that there is a distinct generative tissue in the prothallium of 
Sequoia sempervirens . 
It is interesting to note that Arnoldi has reported a very different 
method of endosperm-formation in Sequoia gigantea . Here the entire 
endosperm is formed in much the same way as in other Conifers described 
by Sokolowa (1891), that is, by means of ‘Alveolen.’ When such great 
difference exists between two species of the same genus, it tends to eliminate 
the endosperm-formation as a means of establishing relationships among the 
Coniferales. 
During the development of the primary prothallium as described 
