ALLOSORUS. 91 



GENUS IV. 



ALLOSORUS. Bernhardt. J. Smith. 



A small genus and yet an interesting one, having barren 

 and fertile fronds dissimilar. The fertile fronds being contracted 

 and having revolute margins, forming, as it were, a universal 

 indusium. 



Veins free and forked; sporangia terminal. 



Sori laterally confluent, round or oval; the sori eventually 

 forming an intramarginal, broad, compound, transverse sorus. 



Fronds bi-tripinnate, or decompound. 



Khizoma creeping and somewhat ccespitose. 



Fertile fronds contracted, segments oval, elliptical, and revolute. 



Sterile frond having the pinnules dentate, crenate, or laciniate, 



Mr. Moore places the Allosorus amongst the Polypodia, and 

 certainly it seems more natural than with Pteris, although it 

 is, perhaps, a genus whose characters are midway between them, 

 and consequently difficult to determine to which to attach it. 



Mr. Smith remarks in his "Genera of Ferns," that having 

 the margin of the fronds membranaceous and indusiiform, the 

 sori being confluent, and forming, as it were, a transverse 

 marginal sorus, it, on this account, approaches near to the 

 genus Pteris; but as the indusiiform margin is formed by the 

 changed state of the fertile frond, and does not rise from a 

 sporangiferous receptacle, as in the true Pteridice, it, on this 

 account, approaches Polypodium, from which its great difference 

 is the contracted character of the fertile fronds. 



Mr. Smith enumerates six species: — 



1. — Crispus, Bernhardi. 



2. — Acrostichoides , Sprengel. 



3. — Brunonianus, ( Cryptogramma, W allien.) 



4. — Gracilis, J. Smith, ( Cheilanthes , Kaulfuss.) 



5. — Ciliatus, Presl. 



6. — Hirsutus, Presl. 



None seem to be cultivated in this country except the 

 solitary indigenous species, the Allosorus crispus. 



vol. m. x 



