88 Campbell. — On the Prothallium and Embryo of 
ship existing between the Equisetineae and Filicineae from a 
study of the one surviving genus of the former class is of course 
plain, especially as there is every reason to look upon this 
genus as a degenerate one. Nevertheless, the evidence seems 
strong enough to warrant the assumption of a closer relation- 
ship between the two groups than is usually admitted, even 
perhaps to unite the two groups into a single one opposed to 
the Lycopodineae. 
In the course of these investigations I have seen no reason 
to change the opinion already expressed *, that the eu- 
sporangiate, and not the leptosporangiate ferns, are the 
primitive forms. Since this was written, Prof. Bower 1 2 has 
admitted the force of the arguments then brought forward, 
and has himself added a very weighty argument in favour 
of this view based upon geological evidence. The great 
majority of carboniferous and pre-carboniferous ferns 3 appear 
to have been allied to the Marattiaceae, and there is evidence 
that the Ophioglosseae also existed ; but if the latter were 
like their living descendants, the soft nature of their tissues 
must have prevented their preservation in a fossil state in any 
but the most exceptional conditions. Sporangia referable 
to the Osmundaceae also occur ; but, according to Solms- 
Laubach 4 , no true leptosporangiates occur before the Mesozoic. 
The simpler living Ophioglosseae probably resemble the 
primitive ancestral forms from which the other ferns have 
sprung. From this primitive stock we may assume that very 
early the Equisetineae arose, and later the Marattiaceae, both 
forms culminating in the carboniferous. The latter group 
probably gave rise to forms like Isoetes through which the 
Angiosperms later developed. A third group, the Leptospo- 
rangiatae, derived from the Ophioglosseae through forms like 
Botrychium and Osmunda , are the prevailing ferns of modern 
times, and at present constitute a vast majority of living 
1 The Affinities of the Filicineae, p. 5. 
2 Annals of Botany, Vol. V. no. xix. 
3 Solms-Laubach, Palaeophylotogie, p. 146. 
* L.c. p. 157. 
