236 CHAEACTEES OF TEIBES AND GENEEA. 



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. CYSTOPTERIS, Sernh. (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. Indusium 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. 



OBS. 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 

 to 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. 



With the exception of C. montana, all the species have 



