481 
Polygonum tenue var. microspermum Sheld. |. c., not Engelm. 
Polygonum Engelmanni Sheld. |. c., not Greene. 
Specimens of P. /enue from Minnesota have lately been errone- 
ously referred to P. microspermum,* and to avoid further confusion 
of the geographical range of the latter species, I take this means 
of correcting the mistake. Taking into consideration the fact that 
_P. microspermum is a characteristic plant of the highest mountains 
of Middle Colorado, where it has been collected only two or three 
times and at stations not widely separated, and then taking into 
consideration the laws of geographical and altitudinal distribution, 
We should not expect to find the species at a comparatively low 
altitude in Minnesota. F urther, an examination of the specimens 
on which Mr. Sheldon based his determinations shows them to 
lack all the essential characters of P. mucrospermum, and to possess 
all the essential characters of P. “enue. Selecting a few of the 
more prominent characters, we see that P. microspermum, like P. 
Douglasii, has a flat leaf. P. tenue has leaves with two lateral 
impressions on either side of and parallel with the midrib. They 
also differ much in shape from those of P. microspermum, The 
pedicels of the latter species are slender and deflexed, even in 
flower, whilst those of the former are short (sometimes almost 
Wanting), stout and always erect. The achene of P. mcrospermum 
1s oblong or oblong-ovoid, smooth and shining; that of P. zenue is 
Strictly ovoid, granular on and about the angles, smooth and shin- 
Mg only at the centres of the faces. The Minnesota specimens 
referred to, collected in Chippewa county, possess all these charac- 
ters of P. zenue, and others, into whose details it is unnecessary to 
€nter, as the manner of branching, the texture, flowers, ocrez, etc. 
Potyconum CRISTATUM Engelm. & Gray, Bost. Journ. Nat. Hist. 
5* 259 (1847). 
Only three stations for this rare and interesting species were oe 
nown up to this season. Two of these were about Aiken, South 
Carolina, while the original was in Texas. While collecting in 
Middle Georgia this season I met with the plant, first at various 
Points on the slopes of Stone Mountain, and subsequently encoun- 
tered it in the Yellow River Valley and about Logansville. This 
cag ’ ‘ ; 4 
* Bull. Geol, and Nat. Hist. Surv. Minn, 9: nee 
