40 Lang. — Prothalli of Ophioglossu m pendulum 
(Fig. 58) of cells, each row consisting of about six cells, some- 
what flattened parallel to the surface. The cells of the neck 
turn dark brown in old archegonia. The central series could 
only be imperfectly made out : there is a large ovum, but the 
number of canal-cells could not be determined. From the 
arrangement of the cells at the base of the ovum, it seems 
probable that a basal cell will be distinguishable in the 
developing archegonium. The possibility of some slight 
distortion due to the growth of surrounding cells must 
of course be borne in mind in considering the structure of 
such old archegonia, but was probably inconsiderable in the 
example figured. 
A number of archegonia had apparently been simultaneously 
fertilized on a few of the prothalli which were attached to 
young plants. The preservation of the arrested embryos, 
which were present in addition to the plant, was not good 
enough to make a study of the segmentation possible. It 
was however clear that, as in Botrychium , the young embryo 
soon becomes deeply seated. The larger embryos present 
on the prothalli represented in Figs. 35-37 were all about the 
same age. One of them is represented in approximately 
median section in Fig. 59. The large hemispherical foot is 
deeply inserted in the tissue of the prothallus. The upper 
portion of the embryo had burst through the covering layers 
of the latter ; in it can be distinguished the primary root (r) y 
the median plane of which fell in another section of the series ; 
the first leaf (/), the tip of which is injured, and, (covered over 
by the sheath of the first leaf), the depressed apex of the stem 
( st .). The position of the organs of the embryo is thus essen- 
tially similar to what is found in Botrychium virginianum . 
The apical region of the stem of the embryo of Helmintho- 
s tacky s is shown in Fig. 60. At the base of the depression 
filled with hairs the initial cell is visible, and segments can be 
seen to have been cut off parallel to the sides and the trun- 
cated base. 
