566 PLANTiE JAVANICiE RARIORES.
as being readily distinguishable by the sorus originating at the point of confluence of several veins.
With respect to Dipteris, the section to which our plant belongs, there is no difficulty in distinguishing it from all other groups of Polypodium, and particularly from that now alluded to, if the dichotomous ramification of the primary veins be admitted into its definition. And as that ramification may be said to be necessarily connected with the peculiar division of the frond, this section, so con- stituted appears to rest on characters at least as important as those of several groups at present generically distin- guished from Polypodium, as Cyclophorus, Pleopeltis, Adeno- phorus, and even Grammitis, Selliguea, and Meniscium.
If, however, the dichotomous primary veins are left out of consideration, no sufficient character remains to distin- guish Dipteris from that section of Polypodium, including P. quercifolium, diversifolium, and several other species, and which M. Bory has established, chiefly from the pre- sence of dissimilar sterile fronds, as a subgenus under the name of Drynaria. But the existence of these sterile fronds being neglected, Drynaria cannot be separated from that more extensive section comprehending P. phymatodes, lycopodioides, &c, and to which (including Drynaria) I have referred in my observations on Matonia, in Dr. Wallich's Plantde Asiaticce Rariores}
These three subdivisions of Polypodium agree in having their sori placed on the point of confluence, or perhaps sometimes of divarication, of several branches of the anas- tomosing veins ; and Dipteris being distinguished by its dichotomous primary veins, the remaining two sections may form one subgenus, for which the name proposed by M. Bory may be adopted.
In many species of Drynaria so constituted, the prin- cipal vein of the sorus is manifestly that in which the ten- dency to produce capsules is generally the greatest in the natural order ; namely, the lowest branch of the upper or inner side of the primary vein, or that branch which in the appendix to Captain Plinders's Voyage 2 is considered as
1 [Ante, p. 543.] 2 [Vol. i, p. 60.]
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