BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 173 
areolae, for in the pluriseriate type of venation these are true 
homologues of the costal and only areolae in Vittaria. Anantha- 
corus might better be considered as included in Polytaenium rather 
than in Vittaria, but the definitely localized fruiting lines, which 
are never so definitely localized in Polytaenium, furnish adequate 
ground for generic separation. 
The venation as figured (PLATE 2, FIG. 3) is of the ordinary 
pluriseriate type described for Polytaenium. The scales are clath- 
rate. The sporangia are in shallow grooves (PLATE 2, FIG. 2). 
The spores are diplanate. Pyriform capitate paraphyses of an 
ordinary sort are present. 
6. ANETIUM Splitgerber, Tijdschr. Nat. Gesch. 7: 395. 1840. 
(PLATE 2, FIG. I) 
Type species, Acrostichum citrifolium L. (Type specimen from 
Martinique.) 
Anetium, with a single species, A. citrifolium, has long appeared 
an anomalous genus and its proper position as regards other ferns 
has been in question, but I think I have here sufficient evidence 
to locate it properly. 
Its venation is of the Polytaenium type in its highest develop- 
ment and does not need further discussion, neither do its other 
characters of vestiture, spores, or epidermal cells, all of which 
agree with the general types characteristic of the tribe. 
Only the arrangement of the sporangia has caused uncertainty 
as to its systematic position. The sporangia have always been 
described as occurring only over the parenchyma within the 
areolae, and this is certainly the ordinary position. This has 
naturally resulted in placing the genus with the Acrosticheae, 
in which such sporangial position is the rule. In the Underwood 
Fern Herbarium, however, is a specimen which shows the varia- 
tion in soral position indicated in the figure (PLATE 2, FIG. 1). In 
the lower part of the leaf the sporangia are along the veinlets in 
rather complete reticulation. Farther up this passes over into 
the usual Anetium type, but this single specimen is enough to 
show that the Anetium type has probably been derived from the 
Polytaenium type and that Anetium may be definitely and properly 
located in the Vittarieae. 
