443 
Botrychium simplex , Hitchcock . 
acropetal succession for a long time. While the archegonia are somewhat 
later in making their appearance, still the first ones are formed while the 
gametophyte is still very young. They do not develop upon the median 
ridge, but form a line on either side of it (Plate XVI, Figs, i, 2, 5, 6 ). 
Sections of the gametophyte (Figs. 3, 5) show it to be composed of 
nearly uniform parenchyma, which in the older portions of the thallus 
is infested with the characteristic endophytic fungus found in all the 
Ophioglossaceae. In B. simplex the endophyte seems to be somewhat 
less uniformly distributed than is usually the case, and a good many cells 
of the infected area are nearly or quite destitute of the fungus, while in 
others the hyphae form dense tangled masses or clumps within the cell. 
No special study was made of the endophyte, as there was no indication 
that it differs materially from that which has been described in other species. 1 
As usual, the fungus is confined to the older tissues of the gametophyte 
and does not invade the meristematic tissues, nor the immediate vicinity of 
the reproductive organs. 
The apex of the gametophyte shows a well-marked growing-point 
(Fig. 3, x). This is slightly inclined towards the dorsal surface of the 
thallus, the ventral tissue extending somewhat beyond it. In several cases 
there was evident in median sections a cell (Fig. 4, x), which, from its form 
and position, closely resembles the apical cell of many liverworts, and 
probably is the definite simple apical cell of the thallus. No successful 
horizontal sections of the growing-point could be made, so that the exact 
form of this apical cell was not determined. 
Antheridium. 
As will be seen from the figures, the first antheridia appear very early, 
and others arise in acropetal succession for a long period. They agree 
closely with those of the other species in their development 
The first division in the mother-cell separates an outer, or cover-cell, 
from an inner one which gives rise to the mass of spermatocytes (Figs. 7, 8). 
The cover-cell undergoes a series of divisions by vertical walls, and most o f 
the resultant cells undergo a transverse division, so that the outer wall 
of the antheridium is composed, for the most part, of two layers of cells ; 
but in one of the cells the transverse wall is suppressed, and this cell 
( 0 . in Fig. 9) becomes the operculum, which is destroyed when the 
antheridium opens and allows the spermatozoids to escape. 
The operculum, seen from the surface (Text-fig. 2, B), is nearly square, 
but occasionally there is a suggestion of the triangular operculum found in 
Ophioglossum , 2 a condition also occasionally found in B. obliquum . In the 
latter species, two opercular cells are not uncommon, and Bruchmann shows 
1 See Jeffrey, loc. cit. ; Campbell, The Eusporangiatae. 
2 Campbell, The Eusporangiatae, Figs. 12, 13. 
I i 2 
