1893.] Botany. 281 
inary List of American Species of Polygonum” in the Torrey Bulletin _ 
for December Mr. John K. Small enumerates seventy-nine species. 
Some changes are made in the nomenclature, and two new species (P. 
mexicanum and P. pringlei are described from San Luis Potosi, Mex- 
ico.)—* Amherst Trees,” by Professor J. E. Humphrey, and “The 
“Woody Plants of Manhattan in their Winter condition,” by Professor 
A. S. Hitchcock, are two pamphlets: which indicate the increasing 
interest in forest trees as constituents of the flora of a locality. The 
first named is the more popular and treats of many New England 
trees from the standpoint of the tree lover and the landscape gardener ; 
the second is quite scientific, and is intended to aid the people of the 
plains (Kansas) to identify trees in their winter state-——A. W. Bennett 
has published in the “St. Thomas Hospital Reports ” (London) a use- 
ful paper entitled “ Vegetable Growths as Evidence of the Purity or 
Impurity of Water.” He discusses the subject under four heads, as 
follows: I. Flowering Plants; IJ. Fungi; IIL Alge ; and IV, Char- 
aces, The presence of the first is “a sign of comparative purity of 
the water;” of the second of the impurity of the water. The blue- 
green algæ (Cyanophycew) “should be regarded as rendering it (the 
water) unfit for domestic purposes.” . The chlorophyll-green algæ 
( Chlorophycee) are probably innoxious, in spite of the prevalent opin- 
ion to the contrary. The Characee are regarded as noxious “since 
when decaying they give off a strong fetid odor, accompanied by evo- 
lution of sulphuretted hydrogen gas.” 
