BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 179 © 
This is shown in the figures of the cross-sections of the leaf. 
(Compare PLATE 5, FIG. 6, with PLATE 7, FIG. 9, 10.) 
POLYTAENIUM CAYENNENSE (Desv.) Benedict (PLATE 6, FIG. I) 
Polytaenium cayennense merely represents the twin net vena- 
tion in its complete development. All stages between it and 
Polytaenium quadriseriatum are presented by other species of the 
genus (PLATE 7, FIG. 3-6), and the same type is characteristic 
of Ananthacorus (PLATE 2, FIG. 3) and Anetiwm (PLATE 2, FIG. I). 
The two remaining genera offer venation patterns which at 
first sight appear to find no place in the series just presented, but 
represent rather a divergent series. Their exact relationship can 
be best shown when the ontogenetic stages are taken up. Their 
types may be designated sufficiently by the generic names alone. 
HectstopTeris J. Smith (PLATE 4) 
PLATE 4 includes so many divergent leaf forms that it might 
at first sight appear advisable to employ more than one type name 
to characterize the different developments. These, however, all 
depend merely on the number of divisions of the leaf trace and 
are not recognized as distinctive of species, so that the number 
of types would be a matter of arithmetic. The ecistopteris type 
then may be considered as including all forms that show a free- 
veined dichotomy of the leaf trace. It should be noted in passing 
that such Hecistopteris leaves as are represented by FIGURES 19, 
20, and 22, of PLATE 4 are exactly analogous, as to the stage of 
development, with the Monogramma subfalcata stage. Similarly, 
the Vittaria sikkimensis stage is well represented in Hecistopteris 
by FIGURES 2, 9, and 15 of PLATE 4. 
AntropHyuM Kaulf. 
The Antrophyum type of venation is essentially that of Hecis- 
topteris, but with the veins anastomosing to form areolae. This 
can be easily understood by comparing the venation of Antro- 
phyum nanum (PLATE 2, FIG. 6) with that of some of the larger 
Hecistopteris leaves (PLATE 4, FIG. 4). In the larger species of 
Antrophyum the contiguity of the numerous veins so modifies the 
scheme as to make the dichotomy hard to trace. This modifi- 
