CHARACTERS OF TRIBES AND GENERA. 163 



tracted ; pinnae rachiform. Venules evident contiguous, 

 parallel, and sporangiferous nearly their whole length. 

 Sporangia confluent, forming a broad, transverse, compound 

 sorus. Indusium narrow, attached on the interior edge of 

 the margin, involute. 



Type. Acrostichum triquetrum, Wall. 



OBS. In my herbarium Acrostichum triquetrum of Wallich 

 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 allusion 

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

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

 generic character I consider it not worthy of consideration. 



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, but 

 are destitute of squama? 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 from the costa, and bearing the sporangia nearly 

 their whole length, sufficiently distinct to be viewed as 

 linear sori, similar to that of Gymnogramma, but differing 

 in being furnished with a re volute indusium as in Lomaria. 

 Under these circumstances I find it difficult to determine 

 its natural position ; the character of the fertile pinnae, 

 however, indicates its affinity to be with Llavea. 



Sp. P. triquetra (Wall.) (Bedd. F. Brit. Ind., pi. 165) ; 

 P. adnata (Bl.\ Bedd. F. Brit. Ind., pi. 51 (Hook. Sp. Fil. t 

 3, t. 147) ; P. glauca (Bl.), Bedd. F. Brit. Ind., pi. 90 ; 

 P. pycnophylla (Kze.\ Bedd. F. Brit. Ind., pi. 52 (Hook. Sp. 

 Fil., 3, t. 148); P. euphlebia (Kze.) (Hook. Seed. Cent., t. 

 89) ; P. biserrata (Mett). 



