4 AMERICAN MIDLAND NATURALIST 
it that it contained no mention whatever of the latter species nor 
of any other varieties whatever. In fact almost at the very 
opening of his article he says: “Le Polygonum amphibium ne 
varie guére; il ne presente, a ma connaissance, ni variétés, ni races.” 
In spite of this I found it asserted without the least hesitation in 
the Symposium that “P hartwrightw{~ can be developed at will 
by growing P. amphibium on land instead of in water.’”’ Dr. Cowlest 
does not tell us what warrant he has for such a statement, whether 
the result of investigations of his own not as yet published, or that 
the statement was made on the strength of another investigators’ 
conclusions. Massart’s researches were made on the European 
plant P. amphibia and as Dr. E. L. Greene* has shown this is 
a distinctively Old-world plant, not found in America, and that 
our plants have in all their phases characteristic, and distinctive 
marks by which they may readily be distinguished from the P. 
amphibia of Europe. As far as the ecological import of Massart’s 
work on P. amphibia is concerned most of his results were known 
over 200 hundred years ago, and when these are made to be the 
principal part of his paper, one overlooks entirely the anatomical 
researches which are really the characteristic part of the article; 
for every thing in it centres around them for its originality. It 
would, to say the least, be very unsafe to draw conclusions about 
our American plants before it has been definitely ascertained that 
they are specifically identical with the old world Persicaria amphibia. 
Dr. Gray can hardly be accused of being a reckless species 
maker, and such an implication need hardly have come from the 
editors of the New Manual, which would certainly seem to be the 
case in regard to the suppression of P. Hartwrightw therein. They 
+ P. Hartwrightii would be more correct. 
t ‘One of the noblest aims of ecology is the destruction of many of the 
“species” of our manuals. Where the critical study of species is confined 
to the herbarium it often happens that ecological varieties or habitat forms 
are given specific rank. An excellent instance of this is seen in the case of 
Polygonum amphibium and P. hariwrightii. ‘The latter, which looks wonder- 
fully different from the former in herbaria, can be developed at will by 
growing P. amphibium on land instead of in water. Not infrequently a 
plant may be found on the edge of a pond, showing branches that would 
be regarded as P. hariwrightiz.- Symposium 1. c. p. 266. H. C. Cowles 
‘‘An Ecological Aspect of the Conception of Species.” 
* EK. L. Greene. Leaflets of Botanical Observations and Criticism, 
Viole 2m. ‘1904. pp: 24) (25. 
en 
