986 CHARACTERS OF TRIBES AND GENERA, 
the fronds, they nevertheless all agree in general aspect 
with Phegopteris and Lastrea, differing only in the sori 
being furnished with a calyciform indusium. 
125.—Cystopreris, Bernh. (1806). 
Polypodium, Linn. ; Aspidium sp, auct. 
Vernation fasciculate or uniserial. Fronds slender, lan- 
ceolate, bipinnatifid, 6 to 15 inches high. Veins forked ; 
venules free, Sori punctiform, lateral. Indusiwn cucul- ` 
late, interiorly attached. 
Type. Polopodium fragile, Linn, 
Illust. Hook. and Bauer Gen. Fil, t. 52, B ; Schott. Gen. 
Fil. fig. 8; Moore Ind. Fil, p. 73, A; J. Sm. Ferns, 
Brit. and For., fig. 76; Hook, Syn. Fil., t. 2, fig. 19. 
Oxs.—This genus contains low growing Ferns, with the 
general character of the small species of the Lophidium 
section of Lastrea, but it is technically distinguished by the 
indusium being short, ovate, or oblong, and vaulted, so as 
io form a cucullate marsupial cyst, opening exteriorly. 
It has also some claims of relationship with Athyrium; but 
the base of attachment of the indusium being across the 
venule—not longitudinally along one side as in that genus 
—indicates its natural affinity to be with Lastrea. 
Representatives of this genus are found widely spread 
over the northern part of Europe, Asia, and America, even 
to within the Arctic circle, and also in several localities in 
the southern hemisphere. The different appearances of 
Specimens and observation of living plants from different 
localities, have given rise to at least twenty species being 
described by various authors; but careful examination : 
reduces that number to the following. 2 
With the exception of C, montana, all the species have - 
