79 
proach most nearly the liverworts. In the two former a truly 
dichotomous branching, apparently entirely similar to that in the 
thallose liverworts, has been recorded by Goebel* and Jonkman.t 
CONCLUSIONS. 
From a consideration of the facts presented above, it seems 
that we are justified in assuming a direct relationship between the 
Filicineze and the Hepatice. The close correspondence in the 
development of the two groups, as well as the structure of the 
thallus in the simpler liverworts, indicates that the two groups 
have had a common origin, and that the Filicinee branched off 
from the liverworts at a comparatively late stage. Probably 
originating from filamentous green algz (or possibly flattened 
forms like Coleochete), the next stage was a delicate heart-shaped 
form with two-sided apical cell, as in the young fern-prothallium 
and such liverworts as Metzgeria and Aneura. A thickened 
midrib was probably early developed, and in the more differentia- 
ted forms the whole thallus became several cells in thickness and 
in the Marchantiacee especially, of considerable complexity. 
It is not my purpose to speak of the affinities of the different 
groups of liverworts here, as that has already been ably discussed 
by Leitgebi. It may, however, be well to consider briefly the 
relative positions of the ferns, as indicated by a comparison with 
the liverworts. Of the forms that have been investigated, the 
prothallia of Osmundacez§, and Marattiacez,|| resemble most 
nearly such liverworts as Dendroceros and Pellia, and are proba- 
bly the most primitive. The Gleicheniacee,° resemble the 
Osmundacez, in many respects and are in certain ways a con- 
necting link between them and the Polypodiacez, with which the 
Schizeeaceze closely agree. The Polypodiacee, with the 
Cyatheacez, form the end of the homosporous series. The 
Hymenophyllacee seem to be degenerate forms, and our present 
knowledge would indicate that they branched off pretty low 
down—possibly between the Osmundacee and Schizaacee. 
* Goebel, Gymnogramme Leptophylla, etc. Bot. Zeit. 1877. 
+ Jonkman, La Generation sexuée des Marattiaceés, p. 208. fig. 57: 
fl. c. Vol. VI. pp. 49-53. 
§ Kny, 1. c. Luerssen (Schenck’s Handbuch P 171.) 
_ | Jonkman, I. c. 
- ° Rauwenhoff, La Generation sexuée des Gleichéniacées. 
