174 BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 
The stem is much more elongated than in any other member 
of the tribe, the leaves being far apart. Judging from the peculiar 
stele, Anetium represents the greatest degree of modification in 
the whole tribe. 
7. ANTROPHYUM Kaulfuss, Enum. Fil. 197. 1824 
Type species, Hemionitis reticulata Forst. (Type from Upolu.) 
The genus Antrophyum, as properly limited to the Old World 
plants having pluriseriate venation, includes approximately 
twenty-five species. This number is in excess of that given by 
Christensen, but it was determined after a careful study of material 
which contained nearly all the species described, and the estimate 
is conservative rather than excessive. The genus includes all the 
Old World species of Vittarieae having more than two rows of 
areolae through the leaf. 
The origin and arrangement of the areolae is, as noted under 
Polyiaenium, quite different from the type characteristic of that 
genus. Instead of proceeding from the midvein at regular inter- 
vals, as in Polytaenium, they are all directed toward the base and 
arise by the dichotomy of basal veins. Moreover, even when 
compared with the narrow types of Polytaenium, there is a consider- 
able difference shown. In Antrophyum, areolae laterally adjacent 
to each other usually are practically equal in origin and length. 
In Polytaenium, on the contrary, especially in the narrow species, 
the areolae of the second row are always much shorter than those 
of the first, and are plainly secondary and derivative when com- 
pared with the first (PLATE 7, FIG. 2). 
This difference between Antrophyum and Polytaenium is well 
illustrated in PLATE 6, FIG. 1 and 2. In Antrophyum plantagin- 
eum, the areolae decrease in size from the base toward the apex; 
in Polytaenium cayennense, the decrease takes place from the mid- 
vein outward. 
It has already been noted that some species of Antrophyum 
possess an incomplete axial vein. This is especially evident in 
A. semicostatum, in which the midvein or “costa” may extend 
upward through half or even somewhat more of the lamina, but 
this species does not, on this account, serve to connect the Antro- 
bhyum venation pattern with that of Polytaenium. The midvein 
