88 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
The differences between Nymphaea advena and N. americana (under the specific 
name of variegata) have been discussed by Miller in the Proceedings of the Biological 
Society of Washington, but it is worth while to repeat them here. The most striking 
difference existing between the two is found in the shape of the petioles. In N. advena 
these are subterete; in americana they are conspicuously flattened and there is a median 
ridge, a continuation of the midrib, running along the dorsal surface. This difference 
in petiole structure has an important effect upon the leaf habit of the two species. 
When the leaves of advena first appear in the spring the petioles are comparatively 
weak and the blades are often found floating upon the water; sometimes, however, 
when the plants are growing in mud or in very shallow water, especially when sub- 
jected to the action of tides, the blades are erect from the first. Almost invariably in 
the typical form, as the leaves become older the blades are held stiffly erect. In 
americana the weakness of the petioles, due to their flattening, makes it impossible for 
the blades to be held erect, hence they are always floating, or, if the water in which 
they are growing is lowered, they lie flat upon the mud. Asa consequence of this 
difference in habit, americana, driven away from very shallow water probably by 
injury following its drying up, is usually found in comparatively deep water; while 
advena, able to live in ground which is even moderately moist, clings to the shores, 
or even retreats to the moist meadows bordering streams and ponds. 
Habit is not the only respect in which the two plants differ. The outline of the 
leaf blades is so striking that it is almost always possible to separate the two plants 
certainly from herbarium material. In advena the lobes of the leaves are always 
pointed while in americana they are broadly rounded. The flowers, too, show 
apparently constant differences. Those of the latter species are usually somewhat 
larger. In addition to this the flowers of americana have the inner surface of the 
sepals blotched with red near the base, while in advena the corresponding region is 
normally shaded with green, and only in rare instances tinged with red. 
The fruit of americana is smaller, less strongly ribbed, and is usually tinged with 
red, while that of advena is uniformly green throughout. In the former the most 
common number of stigma rays is 12 while in the other species it is 16. 
The ranges of the two plants, as well, are rather clearly marked. Nymphaea ameri- 
cana is confined to the northern part of the United States and eastern Canada, extend- 
ing as far south as Pennsylvania. Nymphaea advena is confined to the southern United 
States, extending northward into New Jersey and southern New York. In the central 
States we know less of the ranges but all the data accessible indicate that the ranges 
there are what we would expect from conditions in the east. Thus it will be seen 
that americana is usually restricted to the Boreal and Transition zones while advena 
occurs in the Upper Austral. 
The range of advena in the extreme Southern States seems rather peculiar. Perhaps 
it would appear less so if we had fuller material from all parts of the range. The 
species is most common from eastern Pennsylvania south through Maryland and 
Virginia to northern Florida. We have seen no true advena from any of the Gulf 
States west of Florida. The plant has been reported from most of these States, but 
such material as we have seen is referable to species here described for the first time. 
Tn fact we are not certain that the plant appears again until we reach the Rio Grande 
region of western Texas. Here this same species is found in at least two localities. 
Fresh material which we have secured offers no means of separating this extreme 
western plant from the form so common in Pennsylvania and Virginia. Farther 
south, in Mexico, a plant is found which is apparently the same, though the driéd 
material that we have seen shows that the leaves of the Mexican plant are more acute 
than those of the typical form. 
Still farther west the plant has been reported again, this time in California. We 
have seen only dried material from that State, hence can not be sure as to its identity. 
It is probable that it is merely an abnormal form of Nymphaea polysepala. 
