I 2 I 
the more primitive type in the Ferns f 
figures the fact that in these plants, both antheridia and 
archegonia are found on both surfaces, though they are more 
numerous on the lower. 
As regards the sexual organs themselves there is a nearer 
correspondence between the Eusporangiate Ferns and the 
Liverworts than is to be found between the Leptosporangiate 
Ferns and the Mosses. I have elsewhere pointed out 1 that in 
the Eusporangiate Ferns the sexual organs are deeply sunk 
in the tissue of the massive prothallus, a position sufficiently 
distinct from that of the freely exposed and projecting organs 
of the Hymenophyllaceae. The same is the case with certain 
of the Thalloid Liverworts, and especially in the Anthocero- 
teae. D. Campbell 2 has drawn attention to the fact, de- 
monstrated by Jonkman, that more than a single canal-cell 
is present in the archegonium of the Marattiaceae, a character 
in which, according to our present knowledge, they alone 
among the Vascular Cryptogams compare with the Bryo- 
phyta : it may also be noted that the embryo of Marattia 
assumes a vertical position of the axis from the first, accord- 
ing to Luerssen 3 ; but this is a point to which too much 
importance should not be attached. Do what we will by 
drawing comparisons based on such points as these, the 
difference between any living Fern and any living Bryophyte 
is an uncommonly wide one, and it is almost useless to at- 
tempt to place any view of relationship upon a sound basis 
by comparison of mere details in organisms so widely dif- 
ferent. 
There is however a line of evidence which, though in itself 
not conclusive, will serve to give greater stability to the sug- 
gestion that the Eusporangiate Ferns are the more primitive 
type : I mean the evidence from Palaeophytology : in ap- 
proaching the discussion of such a question as the present, too 
little attention has been paid to this branch. It is hardly 
necessary to premise that as negative evidence it is not 
strong : the fact that certain types of plants have not been 
1 Annals of Botany, vol. Ill, p. 370. 2 Botanical Gazette, 1890, p. 4. 
3 Handbuch d. Syst. Bot., I. p. 582, and Fig. 154. 
