SAGITTARIA AND LOPHOTOCARPUS. 29 
more closely related to the Asiatic than to the European 
forms of sagittifolia. 
Classification according to leaf forms has proved very 
unsatisfactory. After examining nearly two thousand 
herbarium specimens, besides much living material, I have 
found that there is least variation in the form and size of 
the achenium, form of the anthers, pubescence or lack of 
pubescence of the filaments, relative length of fertile and 
sterile pedicels, and within certain limits in the form of the 
bracts. As in most aquatics, the leaves vary through wide 
limits in the same species, and characters founded on leaf 
differences, at least among the Sagittifoliae, are of little 
value. Some reliance, however, may be placed on the 
relative length of the lobes or divisions of the leaf, except- 
ing always in the immature or phyllodial forms. The 
phyllodia themselves are too variable to be of much diag- 
nostic value, though some of our more recent American 
systematists have endeavored to draw specific characters 
from them. Phyllodia are not always present. In some 
species they seem to offer wider differences than the leaves. 
They appear to be formed principally when conditions are 
unfavorable for the development of aerial leaves, and 
whether they are considered degraded leaf forms, or rever- 
sions to a previously existing type, the characters which 
they present have little specific value. 
Intravaginal squamules as noted by Buchenau in Engler, 
Bot. Jahrb. 2: 467 (1882), are present in the Alismaceae 
and allied orders. They consist of from one to three rows 
of very delicate scales attached in the axils of the leaves to 
the dorsal edge of the petiole. They are linear-lanceolate, 
2 to 4 mm. long, colorless, from one to three or four cells 
thick at the base. They may be easily studied on young 
plants of the common VS. latifolia, and will probably be 
found in other species. 
Many or possibly all of our North American Sagittarias, 
in common with the Old World species, form underground 
autumn tubers. These have been observed in S. latifolia, 
3 
