Cupressineae, with special reference to Libocedrus decurrens. 291 
also for the other Cupressineae which I have investigated — there is a single 
layer of jacket-cells. Compared with those of other Gymnosperms these 
cells are poorly developed, being very small, while the walls separating them 
from the central cell are almost as thin as the walls of the ordinary endosperm- 
cells. They become differentiated as jacket-cells quite early — before the 
neck-cells are formed — and soon become filled with a dense cytoplasm, due 
no doubt to the accumulation of food substances, and as a consequence stain 
much more deeply than the neighbouring cells. With the growth of the 
archegonia the jacket-cells divide and increase in number, but their multi- 
plication ceases when the central cells have reached their full size. Many of 
them at this time are binucleate, a peculiarity which has also been observed 
in Taxodium (Coker, ’ 04 ). In Cryptomeria they may even be multinucleate 
(Lawson, ’ 04 ). The general appearance and distribution of the jacket-cells 
may be seen in PI. XXV, Figs. 16, 18, and PI. XXVI, Figs. 25 and 30. 
The relationship of these jacket-cells to the nutrition of the egg has 
been a matter of much discussion for the Gymnosperms in general, especially 
since Arnoldi (’ 00 ) described and figured the actual passage of the jacket-cell 
nuclei through the cell-walls and into the cytoplasm of the egg, thus giving 
rise to the structures known as { proteid-vacuoles.’ This subject has, how- 
ever, been thoroughly investigated quite recently by Slopes and Fujii (’ 06 ) 
in the case of the Cycads, Ginkgo and Pinus , and also by Chamberlain (’ 06 ) 
in the case of Dioon . From the account given by Stopes and Fujii it appears 
that the thick wall between the jacket-cells and the egg is pitted, but each 
pit is closed by a thin membrane which is perforated only by ‘ plasmo- 
desmen.’ They therefore point out the impossibility of nuclei, starch grains, 
or protein grains being transferred bodily from the jacket-cells into the egg. 
They further suggest that the jacket-cells are glandular or secretory, and 
render the storage food of the endosperm soluble and available for absorp- 
tion by the developing egg-cell. In the case of Dioon , however, Chamberlain 
demonstrates a distinct communication between the jacket-cells and the egg 
in the form of cytoplasmic hatistoria. 
While the conclusions reached by these later writers are much more 
rational than any offered by previous investigators, their explanations do 
not seem entirely applicable to the conditions found in the Cupressineae. 
As I have stated above, in this latter group the wall separating the egg 
from the jacket-cells shows very little thickening, and I was unable to 
detect any cytoplasmic communication between them. I should also like to 
point out that in all of the Cupressineae, on account of the grouping of the 
archegonia in a single complex, many of the egg-cells do not come in 
contact with the jacket-cells at all. As clearly shown in Figs. 16, 17, 18, 
and 25 the egg-cells that are centrally situated are surrounded completely 
by neighbouring egg-cells. The cytoplasm of these centrally situated egg- 
cells showed very little difference in the character and quantity of food 
