518 Bower.—Studies in the Phylogeny of the Filicales. 
the insertion of the head. The latter has a continuous series of cells of the 
annulus, but the induration is not continued past the stalk ; moreover, the 
cells opposite the stalk, which are thus thin-walled, are less regular in 
outline than the rest. Laterally there is a stomium which is in a position 
unusually near to the insertion of the stalk, that is, distinctly below the 
equator of the sporangial head. It is more regularly constructed here than 
in Dipteris , being usually composed of four cells; this point is best seen in 
Text-fig. 17, c } which represents an oblique view, with the stomium facing 
b. 
a. 
e . 
Text-figs. 17, a-e. Various aspects of the sporangia of Cheiropleuria. For ^description 
see text, x 80. 
the eye. The c central ’ side of the sporangium is shown in Text-fig. 17, 
where the constriction of the stalk just below the head is very marked. 
Here also the relation of the continuous annulus to the stalk is seen, but 
it is best understood from Text-fig. 17, d , which shows from below the 
insertion of the stalk (shaded), and the way in which the series of cells 
of the annulus extends, though with modified form and without full indura¬ 
tion, continuously past it. The details of the sporangia are, however, not 
rigidly constant; thus the number of the cells of the annulus may vary ; 
such numbers as thirty-six, thirty, and twenty-six have been counted. 
