BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 165 
Vittaria includes probably at least forty species and is the 
largest genus of the tribe. More than half of these are native in 
the Old World tropics, and of these I am unable to give the exact 
number, owing to insufficient material of all except the Philippine 
species. Christensen in his Index recognizes forty-six species, 
of which fifteen are American. Several of these may be reduced 
to synonymy or referred to other genera, but there appear to be 
several undescribed and some others listed as synonyms which 
should be recognized, so that the number of species to be recognized 
will remain about the same. 
According to the tribal description, species of a woody texture, 
with sclerenchymatous tissue, and with dictyostelic vascular 
systems, must be excluded from Vittaria. This will reduce 
Christensen’s list of Old World species by two or three names, 
such as V. minor and V. pusilla. Dr. Christ puts these species 
in Pleurogramma, and there appears to be a close relation to this 
group, but the venation is somewhat different from that in the 
American species, in which it consists of a midvein with free 
pinnate veinlets. In the so-called Old World Pleurogrammas, the 
lateral veinlets form two rows of areolae, which, however, have 
free outer veinlets. Like all other groups of the tribe Poly- 
podieae, these two stand much in need of a realignment. 
The characteristic venation of Vittaria is well shown in the 
figures of V. minima in PLATE 2, FIG. 4 and 5. All the various 
modifications shown in PLATE 5 are easily reducible to this simple 
pattern. The greatest differentiation that takes place has to do 
with the direction in which the areolae are elongated; if in a 
line parallel to the midvein, the type shown in PLATE 5, FIG. I, 
results. This is characteristic of all the very narrow species like 
V. lineata and others, including a majority of the species in the 
genus. The species of this type figured, V. intramarginalis, does 
not begin to show the extent to which this leaf elongation may be 
carried. Leaves of V. lineata, not more than three or four milli- 
meters in breadth, reach a length of one thousand millimeters. 
The veinlets in such cases are much farther apart than indicated 
in the figure of V. intramarginalis. In the other type, the areolae 
are elongated in lines parallel to the first direction of the veinlets, 
that is oblique to the midvein. This results in much broader 
leaves, as shown in FIG. 7, 10, and 11 of PLATE 5. 
