75 
appearance of a group of actively dividing cells almost in the 
center of the embryo below the stem apex. This meristematic 
region is probably always of epibasal origin, but is close to the 
basal wall so that it is possible that it may sometimes arise 
below it. At present, however, the indications are that it belongs 
to the same region as the stem and is always strictly endogenous 
in origin like the later roots (Fig. 1,r). There is soon evident 
@ conspicuous cell trianguler in Angiopteris, as Farmer has al- 
realy demonstrated, but not so definite in form in Kaulfussia. 
The root initial now divides by regular segmentation, and the 
root apex grows rapidly, pushing the underlying foot downward 
and ultimately emerging on the lower side of the prothallium. 
In the meantime the cotyledon grows actively and the embryo 
rapidly elongates vertically. It is difficult to determine whether 
a single initial cell is ever present in the cotyledon, which forms 
a thick protuberance close to the very slightly projecting stem 
apex. As in the typical ferns, growth is more active on the 
outer side of the cotyledon which then curves over the stem 
apex. (Fig. 3). 
The vertical growth of the cotyledon finally ruptures the 
upper surface of the prothallium, and the young leaf whose 
apex has already flattened out to form the beginning of the 
lamina appears above the surface of the prothallium. The 
axis of the cotyledon is almost coutinuovs with that ot the 
toot, so that the young sporophyte may be described as 
bipolar. 
As already indicated, only a portion of the epibasal tissue 
contributes to the cotyledon and stem apex. A very considerable 
part of the epibasal tissue remains large celled like that of the 
primary foot derived from the hypobasal half of the embryo, 
and probably serves the same function, being in contact with 
the prothallial tissue from which it doubtless absorbs water and 
0od for the nourishment of the young sporophyte. This tissue 
merges so insensibly into the tissue of the base of the cotyledon 
and root as to make it impossible to recognize the exact limits 
of these organs. There is some disagreement as to the exact 
