Apogamy in Ferns . 181 
covered by De Bary as long ago as 1878. 1 The general resemblances 
between it and De Bary’s plant seemed to be fairly close, but our studies 
on these varieties of Ferns have convinced us that external features of 
similarity must be accepted only with considerable reserve, as affording 
indications of identity. The two forms of polydactyla varieties of the Male 
Fern, and those of clarissima in the case of the Lady Fern, prove that forms 
remarkably alike, but which have had a different origin, may be in essential 
characters very diverse. And this attitude of caution is justified in the 
present instance. For our plant is not only apogamous, but in a remark- 
able degree aposporous as well. Indeed, it is not known to produce spores 
at alb Whatever its real origin, it is at any rate now a plant essentially 
different from that originally known as cristata , and there is no sound 
reason for regarding the two as phylogenetically connected. 
The plant is a small one, with leaves of delicate, somewhat pellucid 
texture. The vascular strands stop short of the ends of the pinnae, and 
the tracheids branch out in the form of a narrow brush. The leaf margins 
are abundantly provided with mucilage hairs, and very often the cells, 
especially at the ends of the final ramifications of the leaf, grow out in 
a tufted manner resembling the hymeneal layer of an agaric (Fig. 67). 
On detaching the leaf and pegging it down on damp soil under glass, 
prothallia are produced in extraordinary abundance. They spring not only 
from the ends of the pinnules (Fig. 66), but also from superficial cells of the 
leaf (Fig. 68). These latter cells occur singly, and are not restricted to, 
though they are often more abundant in the vicinity of, the vascular strands. 
They are easily distinguished in prothallia that have been pegged down 
for a short time by the dense appearance of their nuclei and protoplasmic 
contents. The prothallia that arise from them are commonly irregular in 
shape, and sometimes assume a bulbous appearance. They did not, in our 
cultures, produce sexual organs or embryos. 
The marginal and apical prothallia are much more regularly heart- 
shaped (Fig. 76), and in fact resemble ordinary prothallia of very delicate 
texture. Antheridia are produced freely, but archegonia have never been 
seen on them, nor do they appear to be formed at all. Most of the regular 
prothallia produce embryos, and occasional examples of tracheid formation 
have been encountered in prothallia that have not borne any embryo. 
The appearance of the embryo is heralded by the formation of a very 
much localized hypertrophy situated just behind the growing-point (Figs. 
74, 75). The cells divide freely, but the protuberance thus formed can 
hardly be described as a cylindrical process, such as is formed in Lastrea 
ps.-m. var. polydactyla , Wills. It is at best but a small excrescence standing 
out from the level of the prothallium, and tracheids very soon make their 
appearance within it. The formation of tracheids is not very definite at 
1 Bot. Zeit., 1878. 
