20 Stopes and Fujii, The nutritive relations of the surrounding tissues etc. 
take to be the natural result of tbeir lesser physiological importance 
in tliis group. Because, as we statecl above the amount of deposited 
food stuffs in the endosperm previous to the formation of the embryo 
is small in Pinus , so that what the egg requires is already to hand 
in soluble forms in the surrounding cells. and the jacket cells have 
not got to be so active in preparing stored food for it: also the 
embryo is so early carried down through the jacket cells into the 
endosperm by the suspensors that the jacket cells can do but little 
for it in comparison with what the jacket cells can do for the 
proembryo of Ginkgo for example. In many of the higher 
Gymnosperms, the differentiation of the jacket cells is not very 
great and they may be but short lived, while in some cases they 
are hardly recognisable as specially different! ated front the 
surrounding endosperm cells. For example in Thuja as described 
by Land 1 ) the jacket cells, which do not seem to be so 
much differentiated as in Pinus appear at the time of cutting 
off of the neck cells, and break down shortlv after fertilization. 
Now in Thuja we found that so little solid food is dejmsited 
in the endosperm that even after the embryo has reached a 
considerable size the quantity of starcli in the surrounding cells is 
very trifling. 
In Land’s 2 ) account of Ephedra he describes in the 
gametophyte a basal “storage’'* region, and an upper archegonial 
region in which all the cells are very feebly organised and the 
jacket cell walls “never at any time tliick, become so tenuous that 
thev can scarcelv be seen and evidentlv offer little resistance to 
d d d 
the passage of food into the central cell’’; these cells break down 
altogether at the time of fertilization. According to our view their 
lack of differentiation is correlated with the fact that the storage 
region is distant front the egg cell and tliey have therefore no 
immediate Service. 
TYe have not as yet had the opportunity of examining all the 
genera of Gymnosperms front this point of view so that it is quite 
possible that exceptions may exist and a well differentiated jacket 
layer be present even when there is no deposition of food near the 
egg; but in such a case there may be some other physiological 
significance for these cells. 
Lp to the present all the workers have laid much stress on 
the nuclei and nucleoli of the jacket cells alone as the direct source 
of nutrition of the egg cell. The facts now brought f'orward shew 
this view to be untenable. Every cell of the endosperm does its 
share of temporaryily storing and passing on the food to the egg, 
though apparently the jacket layer is specially active and it is 
possible that the nuclei of the jacket cells may play some important 
part in the working up of the soluble simpler compounds into 
x ) Land, W. J. G., „A morph. study of Thuja". (Bot. Gaz. Yol. XXXIY. 
1902. p. 249—258.) 
2 ) Land, W. J. G., ,.Spermatog. and oogen. in Epliedra tri für ca L (Bot. 
Gaz. Yol. XXXYLLI. 1904. p. 1—16.) 
