tg10] TWISS—PROTHALLIA OF ANEIMIA AND LYGODIUM 169 | 
prothallia of most of the genera have been investigated, a review of 
the literature shows many points untouched, and much, done some 
years ago without the aid of modern technique, that needs reinvesti- 
gation; (2) much experimental work is yet to be done regarding the 
effect of different conditions upon the morphology of the thallus. 
As a beginning I have attempted the study of some of the Schizaeaceae. 
Historical résumé 
The first report on the prothallium of this group was given by 
Kwy (13) at a meeting of the Gesellschaft naturforschender Freunde 
at Berlin in 1868, where he instanced Aneimia hirta as forming a 
cell plate immediately on emergence of the filament from the spore. 
Burcx (6) confirmed this and added that the apical cell when formed 
was not, as in Polypodiaceae and Cyatheaceae, at the end of the 
thallus but at one side. 
In 1875 Burck (7) made a more extended study of three species 
of Aneimia (A. Phyllitidis, A. fraxinfolia, and A. longijolia), and 
laid considerable stress on the fact that the whole filament, by longi- 
tudinal wall formation, takes part in the formation of the thallus, 
while in polypods this is formed only at the end of the filament. 
He also finds the formation of the further stages of the thallus from 
a lateral cell and a later initial group and attempts to trace the course 
of development here more carefully. As an additional character 
of considerable importance, he gives what he calls the “pousse laterale 
normale,” a lateral wing formed by some prothallia, which often 
becomes thickly covered with antheridia. 
BAUKE in his paper (2) points out that this “pousse laterale 
normale” is only a lobe of the often very irregular male prothallium. 
The first point made by Burck he modifies by saying that in the 
Polypodiaceae and Cyatheaceae longitudinal division does take place 
in several cells of the filament, but always after the wall has appeared 
in the terminal cell, while in Aneimia the cells near the spore divide 
at the same time or even earlier than those at the distal end. The 
lateral position of apical cell and initials is still insisted upon, though 
details as given by Burck are criticized. Neither investigator finds 
anything to mention as especially characteristic in the development 
of the archegonia, and both confirm the account of antheridial devel- 
