1 1 8 Steil. — Apogamy in Nephrodium hirtipcs , Hk. 
neighbouring prothallial cells (Figs. 7 and 8, PI. V). When prothallia are 
grown in weak light a larger proportion develop this light region. An early 
stage in the development of the embryo is shown in Fig. 3, PI. V. In this 
case only a few small superficial cells of the embryo are visible on the 
ventral side of the prothallium. The paler portion, so conspicuous in 
the prothallia represented by Figs. 4, 10, and 11, PI. V, is absent in 
this instance. Sometimes tracheides appear in the portion of the pro- 
thallium just described («, Fig. 10, PI. V), but these are not always 
present at so early a stage in the development of the embryo. The pale 
region is generally differentiated before the prothalliutn has reached its 
maximum size. The growth of the prothallium continues for some time 
even after the apical cell of the primary leaf and that of the primary root 
have been differentiated. 
From numerous sections made of prothallia showing early stages in the 
development of embryos, it has not yet been determined whether a single 
superficial cell only is concerned in the formation of the embryo as described 
by Yamanouchi (1908 c) in N ephrodium molle. The embryo certainly begins 
its development very early and even before the cushion of the prothallium 
has been formed. The details of this development are reserved for future 
investigation. 
The apical cell of the leaf of the embryo is differentiated first, then that 
of the root, and finally that of the stem. The stem rudiment appears between 
the base of the leaf and the prothallium. The root is endogenous. Afoot, 
so far as I have been able to determine, is never produced. 
As the embryo grows it involves a considerable portion of both the 
upper and lower parts of the prothallium. This is shown in Figs. 6 [b and c) 
and 11, PI. V. Fig. 12 of the same plate is a dorsal view of the prothalliutn 
that is represented in ventral view in Fig. 11. The extent of the tissue 
belonging to the embryo can be readily determined from the appearance of 
the cells in a stained section. The cells of the embryo are smaller than the 
prothalloid cells, and their cytoplasmic contents are much denser. The 
nuclei of the embryo are large in proportion to the size of the cells, although 
many appear to be no larger absolutely than the nuclei of the gametophyte. 
The vascular system which develops in the young embryo grows anteriorly 
into the leaf and posteriorly towards the root apex. A vascular strand 
also extends into the anterior portion of the prothallium and in the direction 
of the apex of the stem. 
Multicellular glandular hairs are produced on the young embryo. 
Sometimes similar hairs are borne also on the light region in the neighbour- 
hood of the notch (Fig. 9, PI. V). 
While the leaf usually appears first in the development of the embryo 
(Figs. 13, 14, 15), in some cases the root develops before the leaf (Fig. 16. 
PI. V). In still other cases the leaf and the root appear simultaneously (Figs. 
