166 BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 
These variations in venation are not accompanied by any 
features which would indicate that there is any tendency to sub- 
generic grouping on this basis. In fact there are all intergradations 
between the extremes of both types; the two forms occur in both 
the eastern and western hemispheres, and, moreover, in both the 
natural subgenera into which Vittaria may be divided. 
These may be differentiated as follows: 
Evuvittaria. [Type species, V. lineata (L.) J. E. Smith.] 
Stem dorsiventral, phyllotaxy distichous, leaf trace double in 
all but a few simple species, stem and petioles pale. Spores 
diplanate or triplanate, paraphyses variable. 
Includes most of the species, all the Old World species, and 
more than half those native in America. 
Radiovittaria subgen. nov. (Type species, V. remota F ée.) 
Stem radial, phyllotaxy polystichous, leaf trace always single, 
stem and petioles brown, owing to the highly developed collen- 
chymatous strengthening tissue. Spores diplanate, paraphyses 
always of the Monogramma graminea type (PLATE 2, FIG. 18-20). 
Includes V. remota Fée, V. Gardneriana F ée, V. minima 
(Baker) Benedict, V. stipitata Kunze, and V. Orbignyana Fée; 
also two Bolivian species not yet described. 
These two subgenera show points of difference often considered 
as of generic value but the venation and soriation are alike in 
both, and the needs of descriptive taxonomy are probably better 
served by retaining both groups under the one generic name 
Vittaria. 
The stem externally appears about the same in all species of 
Vittarta. In some of the Old World species the internodes are of 
considerable length, but in most of the species the leaves are close 
together. The difference noted as to the color of the Radiovittaria 
stem is not apparent until the scales are removed. The scales are 
essentially the same in all the species, the only variation being in 
size and amount of thickening in the internal walls. (See PLATE 
2, FIG. 9-I1,17.) Alsoin some species these walls may show gran- 
ular or papillose markings. The spores, as already noted, are 
either diplanate or triplanate. The paraphyses show a number of 
different forms, which are of considerable value in grouping the 
