i79 
Apogamy in Ferns. 
mitoses, but the number of the chromosomes was found to be greater than 
an investigation into the corresponding mitoses of the typical Male Fern 
had led us to expect. It is certainly not less than 90, and we are inclined 
to put it a little higher, 9 6 is probably nearer the actual figure (Fig. 58). 
This number is also met with in the prothallia (Fig. 59), although the 
chromosomes are more difficult to count in those cells than even in the 
spore-mother-cells. 
The prothallia, as the investigations of others, especially of Lang, have 
shown, are normal in appearance. They bear antheridia and a few arche- 
gonia. The latter occur immediately behind the growing-point, and are 
situated upon a rather diffuse cushion. The antheridia are rather small. 
They arise as protuberances from the central part of the wall of a cell on the 
lower surface of the prothallial cells, and at first are easily confounded with 
young rhizoids. The antherozoids, as Dr. Lang remarks, are very active. 
The archegonia are peculiar in that they project considerably above the 
lower surface of the prothallium, and this is doubtless to be correlated with 
their mode of formation. The mother-cell divides at first by walls inclined 
to each other, and thus a young archegonium almost resembles a stumpy 
branch, and its elevated position is accounted for. 1 
The central, ventral, and neck canal-cells appear to be perfectly normal 
(Figs. 6 2, 63), and yet fertilization never takes place. 
The embryo arises as a projection from the lower surface of the pro- 
thallium (Figs. 64, 65 a , d), and we confirm the statement of previous 
observers as to its proximity to an archegonium. We are inclined to regard 
the projection, which forms the first sign of the embryo formation, as the 
equivalent of an archegonium arrested and modified in the earliest stages. 2 
Just as is the case with the archegonia, so also here, the first stage consists 
in the bulging out of one (or possibly more than one) superficial cell which 
becomes marked off from its fellows. This cell is, as has already been 
stated, most often situated close to an archegonium, and usually amongst 
several. It may be even derived from the peripheral cell of an archegonium 
itself, as has been stated by other investigators, but this has very seldom 
happened in our own cultures. The cell in question then divides by walls 
inclined to one another, and so a little patch of tissue, the cells of which 
are arrayed fan-wise in section, is formed. As is well known, the anterior 
portion of the projection develops into the stem-apex, whilst the root is 
formed by the projection backwards through the prothallium, and behind 
the venter of the archegonium, of a strand of cells. The protoplasmic 
contents of the constituent elements serve readily to distinguish them from 
the true prothallial cells around them. An apical cell is ultimately dif- 
1 Cf. the account given for Doodia candata by Heim, Flora, Bd. 82. 
2 Lang has suggested a similar origin for the sporophytic ‘ buds ’ on the prothallia of Aspidium 
angulare var . foliosum multifidum , loc, cit., p. 205. 
