POLYGONACEOUS GENERA. 39 
others roughened with minute short strigose hairs, the midvein 
beneath glabrous in the lower, appressed-muricate-roughened 
in the upper: upper part of stem and the peduncles glandular- 
scabrous; spikes 2 or 3 inches long, stout; bracts muricate- 
scabrous on the back, not ciliate; achenes polished, chestnut 
color. 
Crater Lake, near Flagstaff, Arizona, Aug., 1884, J. G. Lem- 
mon. Probably an aquatic of shallow water, becoming ripa- 
rian. This is a mountaineer of northern Arizona; but more 
southerly stations, in the heated and half-desert regions yield 
other species, of terrestrial habitat, which probably do not con- 
nect with this. 
A diligent study of much material from almost all parts of 
the United States, occurring in the herbaria under the name of 
Polygonum Muhilenbergit, more recently denominated P. emersum, 
has shown that this also is an aggregate of species, some of 
them strongly marked, others less so. They differ one from 
another markedly as to leaf outline and also as to the attitude 
of the foliage, the leaves in some spreading away from the 
stem almost divaricately, but in the greater number being ascend- 
ing or suberect. As to the pubescence, they exhibit not only 
different degrees but different kinds of hairiness; and that of 
the midvein beneath invariably differs from that of the super- 
ficies of the leaf. In both the form and the indument of the 
bracts of the spikes one finds also another set of specific char- 
acters. 
There are also several instances known to me by personal 
observation in which these species, normally of the land, do 
under conditions of accidental submersion of the stem, develop 
floating leaves, and those different not only from those of the 
terrestrial state, but also very different in general from those of 
species normally aquatic. Future observation will probably add 
much to our knowledge of such dimorphic eccentricities in the 
genus. 
WË 
es 
LEAFLETS, Vol. i, pp. 33-48, March 12, 1904. 
