NEW SPECIES OF POLYGONUM. 203 
each node, erect in maturity, closely enwrapping the whole 
achene, this as large as in P. consimile, its faces less regu- 
larly rhomboid, being broadest quite below the middle, the 
whole devoid of puncticulation and very highly polished 
(as in P. Engelmannii). 
Known only as collected by myself in the West Hum- 
boldt Mountains, Nevada, 1 Aug., 1894. An obscure plant, 
though not small, the branches being few and widely 
straggling. 
P. FLEXILE. Strictly erect, branched only above the base 
and somewhat paniculately, 2 feet high or more, the herb- 
age deep-green, glabrous: stem about 8-striate, the lower 
internodes 1} inches long: leaves of main stem 1} inches 
long, elliptic oblong, plane, only very obscurely pinnate- 
nerved above, beneath exhibiting a sharply carinate mid- 
herve only, the margin entire even under a lens; stipules 
very thin and scarious, at length torn to the base into about 
8 segments, these nerved below: perianths solitary, dis- 
tinctly and slenderly pedicellate, often nodding in fruit, as 
-green-herbaceous as the foliage itself excepting an extremely 
narrow whitish margin: achenes black and shining but 
minutely puncticulate, the sides deltoid-ovate, concave. 
Type from the plains near Denver, Colorado, collected by 
myself in 1870. Plant of the size of P. ramossimum, but 
with little or no resemblance to it, the branches being slen- 
der, flexible and paniculately spreading; the hue of the 
herbage totally different and quite like that of ordinary so- 
called P. aviculare 
