160 BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 
native in the Old World tropics. Among these five species are 
two that show the simplest leaf structure known among vascular 
plants. In these the leaf has only a single simple vein (PLATE 3, 
FIG. I, 20) and in one of these two species the whole leaf is only 
2-2.5 cm. long, and scarcely 1 mm. wide. In the other three 
species, the leaf trace may divide once or twice to form one or two 
areolae, but even in these species, the leaves are very tenuous 
(PLATE 3, FIG. 6, 10, 12, 13). 
In characters other than those of venation, the species all 
agree with the tribal description given. The scales are clathrate; 
spicular cells have been recorded, although not all the species 
have been examined as to this character; and the sporangia are in 
indeterminate lines along the vein or veins and are protected 
by being depressed in the leaf tissue. Mixed with the sporangia 
are paraphyses of the type common for the tribe. As it happens, 
these take two forms in Monogramma. In three of the species, 
viz., in M. paradoxa, M. subfalcata, and M. trichoidea, occurs what 
is probably the simplest type of paraphysis in the tribe. The end 
cell, which in other species is usually capitate and strongly colored, 
or otherwise differentiated, is in these three species merely rounded 
off, and hyaline like its stalk cells. The whole structure is often 
hard to distinguish from the pedicels of the sporangia (PLATE 3, 
FIG, 16, 18). 
In the other two species, M. graminea and M. dareicarpa, the 
paraphyses have strongly colored and capitate end cells, which 
collapse in a characteristic way when dried, the end becoming 
depressed so that the end cell then appears like a small bell (PLATE 
3, FIG. 4, 5). Paraphyses of this type are also oo: in Hecistop- 
teris and in one group of Vittaria. 
The spores were seen for all the species but Monogramma 
subfalcata, and are of the triplanate type, and like those of this 
type in the other genera of the tribe. 
Because of the interest which may attach to these simplest 
of all ferns, and the need of exact determinations, a brief descrip- 
tive key is offered. All the species have been adequately dif- 
ferentiated by figure and description but only in separate places. | 
There are good figures of the gross leaf anatomy of four of the 
five species, but for comparison with each other and with the 
