OF ASPIDIEAE _ 135 
the venation. In 1856 Mettenius went back to the Swartzian use 
of the genus including in it practically everything with a superior 
indusium ; in this he was followed by D. C. Eaton in our own 
country, and by Dr. Christ of Basel. 
After this réswié of migration and shifting of generic names 
and limits, if there be anyone who still supposes that the application 
of fern names in the past seventy years is a subject in which there 
has been any considerable degree of unanimity among the “au- 
thorities,”’ or who still doubts the desirability and necessity of 
anchoring generic names to some fixed specific type in accordance 
with some rational principle, he is surely too blind to read history, 
or too slow to be worth waiting upon longer to make up his 
mind. 
The ferns of our own country alone, or of the North Temperate 
zone even, do not form a sufficient series to enable one to judge 
clearly or logically in regard to true generic limitations. It is 
necessary to consider a wider range of species for this purpose. 
The following genera which are represented in America appear to 
us worthy of being retained ; it will be seen that only three of these 
are represented in our Northern States. Certain extra-limital genera 
are also included to round up the system, and these representatives 
of the old-world flora are printed in italics, those of the American 
flora appearing in small capitals. Space forbids more than the 
briefest characterization here as follows :— 
Veins normally free, simple, forked, or pinnately branched. 
Indusium normally absent. 
Sori more or less elongate. LEPTOGRAMMA J. Sm. 
Sori round, punctiform. 
Margins of segments plane, herbaceous. FERGOF ARTS For 
Margins of segments widely inflexed, membranous. 
PLecosorus * Fée. 
Indusium orbicular, centrally peltate. 
Pinnae continuous with the rachis ; texture firm, more or less coriaceous. 
PoLysTICHUM Roth. 
i 1 . 4 . . e 
Pinnae articulated with the rachis, easily caducous; texture thin herbaceous. 
CYCLOPELTIS J. Sm. 
Indusium oval, attached by a central axis to a thickened linear receptacle. 
DIDYMOCHLAENA Desv. 
Indusium cordato-reniform, attached by the sinus. 
___* Plecosorus was established by Fée (Gen. Fil. 150. 1850-52) on Cheslanthes specio- 
Stssimus A, Br.;-which the Kew writers have retained in Cheilanthes. 
