CHARACTERS OF TRIBES AND GENERA. 163 
tracted ; pinnæ rachiform. Venules evident contiguous, 
parallel, and sporangiferous nearly their whole. length. 
Sporangia confluent, forming a broad, transverse, compound 
sorus. Indusiwm narrow, attached on the interior edge of 
the margin, involute. 
Type. Acrostichum triquetrum, Wall. 
Oss.—In my herbarium Zférostichum 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 squamæ and are peculiar in the base of the 
stipes being swollen; as also the fertile segments not being 
farnished 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 revolute indusium as in Lomaria. 
Under these circumstances I find it difficult to determine 
its natural position; the character of the fertile pinns, 
however, indicates its affinity to be with Llavea. 
Sp. P. triquetra ( Wall.) (Bedd. F. Brit. Ind., pl. 165) ; 
| P. adnata. (Bl.), Bedd. F. Brit. Ind., pl. 51 (Hook. Sp. Fil., 
3, t. 147); P. glauca (Bl), Bedd. F. Brit. Ind., pl. 90; 
P pycnophylla (Kze.), Bedd. F. Brit. Ind., pl.52 (Hook. Sp. ? 
Fil., 8, t. 148); P. euphlebia (Kze.) (Hook. Seed. Cent, te 
89); P. biserrata (Mett). T d 
