196 BOTANICAL GAZETTE [SEPTEMBER 
the collections of ovules made from one to two weeks after fertiliza- 
tion. These soon dry up and wither away within the hardening 
testa, so that one would not include them in the later collections 
of material if the testa is first removed. 
The subsequent enlargement of the corrosion cavity to accom- 
modate the growing embryo is unquestionably due to digestive 
enzymes secreted by the embryo itself. The archegonia disappear 
as recognizable structures soon after the primary suspensor has 
fully elongated. The rosettes are usually found pressed against 
the top of the cavity, which now includes the space occupied by the 
archegonia after the latter have broken down. An unfertilized 
archegonium withers away soon after the formation of the corro- 
sion cavity, its place being marked by a shrunken chip of hardened 
protoplasm which is often molded into the shape of the lower por- 
tion and side of this organ. Later this disappears also. 
EMBRYO DEVELOPMENT 
This investigation takes up the development of the embryo 
beginning with the 16-celled stage, which has generally been 
recognized as the end stage of the proembryo. It is necessary, how- 
ever, to consider some of the well known earlier stages, and for 
these facts we will depend upon the results of previous workers 
which have been reviewed in the historical discussion. 
Of the 4 tiers of 4 cells each, the lowest constitutes the embry- 
onal group, each of which is an apical cell of one cutting face; the 
next tier above constitutes the suspensor group, each of which 
elongates to form a primary suspensor cell; the third tier has been 
called the rosette, and its further development has never before 
been followed out; and the uppermost tier of cells, which have 
incomplete walls and are in open communication with the egg, 
sooner or later disintegrate. Fig. 1 shows a longitudinal section 
through the base of an archegonium after the suspensor cells have 
begun to elongate and before any of the cells of the embryonal tier 
have undergone further division. In fig. 38 the embryonal tier 
has given rise to a tier of cells (e,) between it and the suspensor, 
and at the left in fig. 37 an embryonal cell may be seen in anaphase 
of division. 
