52 Lang . — Prothalli of Op/i ioglossu m pendulum 
eusporangiate Ferns. The antheridia might well be derived 
from a type like those of the existing Marattiaceae, the 
multiciliate spermatozoids constituting an additional point of 
resemblance. The archegonia are closely similar in develop- 
ment and structure in the two groups, in both of which a 
basal cell is constantly present. The embryogeny does not 
agree exactly, but the similarities are greater than between the 
Ophioglossaceae and the Lycopodiales. In the Marattiaceae 
no suspensor is present, and the apex of the steqi and the 
primary leaf are derived from the epibasal half, but the 
primary root arises with the foot from the hypobasal half. 
This difference may find its explanation in the need for a large 
foot in a embryo attached to a deeply buried prothallus. At 
any rate an analogous disturbance of the primary members is 
evident when the species of Lycopodium with deeply buried 
prothalli are compared with those, the prothalli of which grow 
on or just beneath the surface. 
To sum up the comparison with the Filicales, the form of 
the prothallus, structure of the sexual organs, and, though less 
clearly, the embryogeny of the Ophioglossaceae are such as 
might be expected in saprophytic forms derived from prothalli 
6f the general type found in the Filicales. On the other 
hand, there appear to be no fundamental points of difference. 
It was mentioned above that there is little to suggest the 
idea of any close relationship between the Ophioglossaceae 
and the Equisetales. The gametophyte of the latter has a 
general resemblance to that of the Filicales. It will be 
sufficient to say here that, while it seems quite possible that 
the Ophioglossaceous prothallus could have been derived from 
the Equisetaceous type, there is nothing to suggest such an 
origin as even equally probable to an origin from the Filicales. 
From the above comparisons it would appear that the 
available evidence points to the origin of the type of prothallus 
found in the Ophioglossaceae from forms not unlike the 
gametophyte of the existing Marattiaceae, though possibly 
belonging to a more primitive group. It would further 
appear that little or nothing indicates an origin from the type of 
