8 Law soit . — The Gametophytes , Fertilization and 
parietal layer was very similar to that which I have studied in Sequoia and 
Cryptomeria. As indicated in Fig. io, the central vacuole increases 
enormously without much perceptible difference in the thickness of the 
parietal layer of cytoplasm, although there is a very noticeable increase 
in the number of nuclei, which shows that free nuclear division proceeds 
during the enlargement of the vacuole. 
During these early stages in the formation of the prothallium con- 
siderable attention was given to the nucellar tissue which immediately 
surrounds it. In Taxodium Coker (’03) describes a distinct layer of large 
cells which surrounds, and persists throughout the growth of the young 
prothallium. It is thought that this layer takes an active part in the 
nourishment of the growing gametophyte, and is, therefore, considered to be 
a tapetum. A similar more or less differentiated tapetum has been found 
during the early stages in the development of the prothallium in the 
Abietineae and the Cupressineae, but seems to be entirely wanting in 
Cephalotaxus . It is also absent in Taxns and Torreya. 
For Cephalotaxus Fortunei Mile Sokolowa (’91) figures a distinct but 
very thin megaspore-membrane. In C. drupacea I was unable to detect 
the presence of a megaspore-membrane about the young prothallium, but 
during the fertilization period and early embryo stages an extremely thin 
membrane was observed. In two other species of Cephalotaxus Thomson 
(’05) was unable to find a trace of this membrane. He also reports that in 
Taxus the megaspore-membrane is very poorly developed. The absence of 
the tapetum and the extreme evanescent condition of the megaspore 
membrane is significant. Indeed, from this point of view alone Thomson 
(’05) regards the Taxeae as the most recent group of the Coniferales. 
After the stage shown in Fig. io the parietal layer of cytoplasm 
increases in thickness, but the nuclei remain on the inner surface near the 
vacuole. The formation of the first cell-walls is not unlike that found in 
other Conifers. The nuclei, instead of dividing freely as heretofore, have 
walls formed between them, thus forming the primary prothallial cells or 
‘ alveoli ’ of Mile Sokolowa (’91). These primary cells are open on the 
inner side and exposed to the sap of the central vacuole. The primary 
cells elongate rapidly and encroach upon the vacuole. Before the complete 
closure of the central vacuole by the inward growth of the prothallial cells 
numerous oblique and cross- walls are formed. These early cross-walls are 
also present in C. Fortunei (Sokolowa, ’91) and Torreya (Robertson, ’04). 
Fig. ii represents a section of the upper half of the prothallium before the 
ingrowing cells have met in the central region. It will be noticed that the 
nuclei are not only distributed on the inner exposed surface but they are 
quite numerous at the periphery of the prothallium. The cytoplasm also 
seems to be concentrated at these two definite regions. Nothing unusual 
was observed in the final formation of permanent prothallial tissue. From 
