84 Campbell. — On the Protkallium and Embryo of 
tissue-systems, are to be regarded as evidences of the primi- 
tive character of the Osmundaceae. 
13. The embryogeny approaches most nearly, among the 
forms investigated, to the less specialized leptosporangiate 
ferns. 
14. More than one embryo may begin to form, but probably 
only one reaches maturity. 
From a study of the points just recapitulated, and a com- 
parison of the two species studied with each other and other 
selected forms, some light, it is hoped, may be thrown upon 
the systematic position of the Osmundaceae. 
O. claytoniana in several particulars seems to connect the 
other Osmundaceae with the true leptosporangiate ferns. 
The usual formation of a protonemal filament in germination, 
and the rare occurrence of a cell-surface at first, as well as the 
method of the establishment of the apical cell, is the same as 
in these forms, while in O. regalis 1 , and frequently in O. cinna- 
mornea , the formation of a cell-surface begins at once. In 
Todea^y it is true, a cell-row may be first formed. On the 
other hand, the strong tendency to branch, shown in the 
young prothallia of O. claytoniana , recalls those of Equi - 
setum. The differentiation of the forward part of the midrib, 
where the archegonia are borne, is probably the beginning of 
the cushion of tissue found in this position in most Lepto- 
sporangiatae and Marattiaceae. 
The frequent formation of a filamentous, protonema-like 
prothallium in this species, so different from the ordinary 
form, is noticeable, and has its nearest approach among the 
Hymenophyllaceae. When we look further, other points of 
resemblance are noted. The large green spores, the hori- 
zontal annulus, the structure of the sexual organs in the 
Hymenophyllaceae, are quite as much or more like the corre- 
sponding parts in the Osmundaceae than like these points in 
the Polypodiaceae. 
O. claytoniana agrees with the Marattiaceae in the strongly 
Kny, 1. c. p. 5 . 
2 Luerssen, in Schenk’s Handbuch, I. p. 171. 
