PELLAEA GLABELLA AND ITS SEGREGATES 79 
narrower, 0. 7-1. 0 mm. wide with a sharply crenulate 
hyaline edge about 0. 1 mm. wide. It generally ends 
0. 5-1. 0 mm. below the tip of the leaflet, though rarely 
extending to the very tip as in P. glabella. The sori 
cover a band nearly 1 mm. wide, and the sporangia are 
very conspicuous in mature fronds. In P. pumila the 
indusium is 0. 8-1. 1 mm. wide, with a somewhat crenu- 
late border about 0. 2 mm. wide. The band of sori is 
somewhat narrower than in P. Suksdorfiana, and often 
extends beyond the point of inflexion of the indusium 
so that part of the sporangia are borne on the under side 
of the indusium. They are accordingly better covered 
and less conspicuous than in P. Suksdorfiana. 
As between the two western species, perhaps the most 
clearly diagnostic characters are found in the spores. 
In an earlier paper® I stated that P. pumila has only 
tetrahedral, and P. Suksdorfiana only elliptical spores. 
Examination of further material has proved this state- 
ment erroneous, though spores of other form are in each 
case comparatively rare. The spores of P. pumila are 
much smaller than those of P. Suksdorfiana even when 
comparison is made between spores of similar form. 
The tetrahedral spores of P. pumila vary from 29 x 38 y- 
47 x 55 uw, the mean size being 39x 45. 5y; the few 
elliptical spores are 36 x 47 u-40 x 55y. The tetrahe- 
dral spores of P. Suksdorfiana measure 50 x 58-61 x 66p, 
the much more abundant elliptical spores are 50 x 58y- 
64 x 80u, with the mean size 58 x 70 p. While the 
extremes of the two species approach rather closely, it 
is to be noted that these extreme measurements apply 
to only a few scattering spores. In no case has the mean 
length of the spores in any mount of P. pumila exceeded 
55 u, or that of any mount of P. Suksdorfiana been less 
than 65. As regards spore characteristics, P. glabella 
occupies a position somewhat intermediate between the 
two western species, but more closely resembling P. 
5 Am. Fern Journ. 7:77. 1917. 
