448 36. BLECHNUM BOREAI.E. [CL. XXIV. 



dark brown to the point, compressed, and an ell in length. 

 The fronds are also lanceolate, pinnated below, deeply halt- 

 pinnated above. The leaflets are linear, opposite, and dis- 

 tant or alternating, pointed, half an inch or more in length. 

 On both sides of the middle rib, on the back, lie the so- 

 ri in continuous lines, and are covered by a membrana- 

 ceous indusium, which opens towards the middle rib. When 

 young, the capsules are petiolated, and have sap-tubes be- 

 tween them. Afterwards they become brown, consist of a re- 

 ticular membrane, and are surrounded by an elastic, jointed 

 ring, by the springing of which, rough, angular seeds are 

 thrown out. In a state of greater maturity, the whole back 

 is so covered with sori, that the more early structure is no 

 longer distinguishable : hence the plant can now be readily 

 classed with the genus Achrostichum, 



Diagnosis and Affiiiitij. 



The older fronds can scai'cely be distinguished from Acrosti- 

 chum, but by attending to the presence of the indusium, which 

 is always persistent at the margin of the leaflets ; but in Aero- 

 stichum it is wanting. The genera Struthiopteris and LornOr- 

 ria Willd. might also be confounded with this plant, were it 

 not that in the former the indusium is formed by the margin 

 of the frond, and is laid in the fonii of scales over the sori. 

 In Lomaria the two margins of the leaf unite continuously 

 over the sori, (Billard. Nov. Hall. t. 246.) Compare Anleit. 

 2. 101. 



Synonymes and Figures. 



Walt-asplenon, Trag. f. 208. b. 



Lonchitis aspera minor, Matth. 661. Dodmi. 469- Dalech. 



1221. Ger. Emac. 1140. Pari.:. 1042. 

 Lonchitis altera Neotericorum, Clus. Hist. 2. 213. Lobel. 



Hist. 475. Ic. 815. Foemina, Tahern. 1190. J. Bauh. 



Hist. 3. 737. 

 Asplenium sylvestre, Dalech. 1217. 

 Lonchitis minor, C. Bauh. Pin, 359- Altera foliis Polypo- 



dii, Moris, sect. 14. t. 2. 



