34 
Lang . — Studies in the Morphology and 
the Filicales we now possess were not before Professor Bower when his 
views were expressed. 
As already indicated, all the additional facts for the Marattiaceae and 
for Helminthostachys support Bower’s primary generalization as to the early 
determination and constant position of the stem-apex. Some facts also 
strongly suggest, though proof is wanting, that the first leaf or cotyledon 
may be derived in some cases from the further growth of the apex of the 
stem, and not be laid down as a primary member independently of the 
apical cell of the stem. If this is so the primary importance of the axis 
would be increased. 
The discovery of a suspensor in a second genus of Ophioglossaceae, 
and also in Danaea among the Marattiaceae, is in favour of Bower’s further 
generalization that the type of embryo with a suspensor may be regarded 
as relatively primitive. It would seem probable that, while the suspensor 
had been suppressed in certain Pteridophytes, it was originally present, at 
least in the Filicales and Lycopodiales. 
Critical consideration of the available facts does not, however, appear 
to me to support the view that the presence or absence of the suspensor is 
correlated with the bulk of the prothallus, or that it is to be explained on 
biological grounds. Thus, within the Marattiaceae the prothallus is always 
fairly massive and green . 1 The prothallus is least massive in Danaea , 
and it is in this genus, as Campbell has shown, that the first division 
in the embryo separates a suspensor from the embryo proper. This is 
not the case in the other genera where the fertilized ovum gives rise 
directly to the embryo proper. There is no change in orientation, the 
axis of the embryo remaining straight, with the shoot-pole turned away 
from the archegonial neck. On further growth the shoot bursts upwards 
through the prothallus and the root vertically downwards into the soil. 
Thus in the Marattiaceae the suspensor seems to be of no particular use, 
and, on the other hand, the change from an embryo with a suspensor to 
one without seems to involve no biological advantage and not to stand in 
any obvious relation to the bulk of the prothallus. 
The same result follows if the Ophioglossaceae are considered. Here 
in all cases the prothalli are relatively bulky and saprophytic. Though, 
owing to the conformation of the prothallus and the direction of the 
archegonia, the embryo cannot grow straight upwards through the pro- 
thallus as in the Marattiaceae, the available evidence is against regarding 
the curvature of the embryo as involving any serious disadvantage. It has 
been shown that it does not prevent the successful growth of the plant in 
Helminthostachys. The suppression of the suspensor thus does not seem 
well explained on biological grounds, though it certainly leaves the way 
1 The fact that the prothallus contains an endophytic fungus does not appear to be of primary 
importance as regards the embryogeny. 
