CHARACTERS OF TRIBES AND GENERA. 163 



tracted ; pinnas rachiform. Venules evident contiguous, 

 parallel, and sporangiferous nearly tlieir whole length. 

 Sjioranffia confluent, forming a broad, transverse, compound 

 sorus. Indusium narrow, attached on the interior edge oi' 

 the margin, involute. 



Type. Acrostkhuin trii'iuetrum, Wall. 



Obs. — In my herbarium Acrostichum trirpietrmn of Wallicli 

 and the species now associated with it long stood as a distinct 

 group of Lomaria, and had also been early noticed as 

 such by Kunze, and afterwards by Mettenius, who separated 

 them as a distinct genus under the above name, in allusiosi 

 to the obliquity of the ring of the sporangia ; but this T 

 find to be only partially the case in one species, and as a 

 generic character I consider it not worthy of consideratioi'. 



Six species are at present known referable to this genus, 

 which in the "Species Filicum " are retained as a section 

 of Lomaria, with which they agree in general aspect, bi:u 

 are destitu.te of sciuamas and are peculiar in the base of the 

 stipes being swollen; as also the fertile segments not being 

 furnished with a transverse anastomose, the venules rising 

 direct fi-om the costa, and bearing the sporangia nearly 

 their whole length, sufficiently distinct to bo viewed ;is 

 linear sori, similar to that of Gijmnofjramma, but differing 

 in being furnished with a revolute indusium as in LuinurUi. 

 Under these circumstances I find it difiicult to determine 

 its natural position ; the character of the fertile pinnie, 

 however, indicates its affinity to be with Llavea. 



Sp. P. triquetra {Wall.) {Bedd. F. Brit. Iiul, pi. 165) ; 

 P. adnata (Bl), Bedd. F. Brit. Ind., pi 51 {Hook. Sp- Fil , 

 3, t. 147) ; P. glauca (I.7.), Bedd. F. Brit. Ind., jd. 'JO ; 

 P. pycnophylla(ir3e.),i;(;(2c?. F. Brit. Ltd., pi. ^S {Hook. Sp. 

 Fil., 3, t. 118); P. euphlebia {Kze.) {Hoolc. Seed. Cent., I. 

 89) ; P. biserrata {Mcti). 



