60 Contributions from the Gray Herbarium 
he failed to state what difference he found between his plant and 
P. canadensis and indeed he brought out no character in his de- 
scription that does not nicely apply to the latter plant! Neither 
Rydberg in his Flora of the Rocky Mountains nor Nelson in the 
Coulter-Nelson Manual mention Heller’s segregate but include 
P. canadensis L. as a component of the Coloradan flora. However, 
in Wooton & Standley’s Flora of New Mexico, U. 8. Nat. Herb. 
Contrib. xix. 597 (1915), we find P. fluviatilis accepted but ac- 
companied, as though by way of apology, by this note: “ Thi 
is closely related to the eastern P. canadensis L., but appears to be 
fairly distinct.’’ One would gather from this that neither Heller 
nor Wooton & Standley found any reliable characters by which 
to separate the plant of the southern Rocky Mountains from the 
more eastern form. And as a matter of fact the western plant 
possesses no characters that are stable or definite enough to cause 
it to be considered specifically distinct. It may, however, be 
treated as a geographical variant. True P. canadensis does not 
occur west of Kansas and Oklahoma, although its range extends 
eastward to the Atlantic. Throughout this area it is uniform im 
its characters and only as it occurs in New Mexico and southern 
Colorado does it display any variation worthy a place in classifi- 
cation. The Rocky Mountain form, occupying as it does a range 
isolated from the western edge of the area occupied by the typical 
state, might therefore be expected to be somewhat different and 
evidently upon the strength of this expectation rather than upon 
the actual discovery of differences Mr. Heller has proposed his 
new species. And indeed only in the character of the corolla, and 
less definitely in the nature of the foliage may the isolated western 
plant be separated varietally. In the typical form the slender 
corolla-tube is only 1.5-2 mm. wide at the base toward which it 
tapers slightly, while the corolla-tube of the western form 1s nearly 
or quite 3 mm. in width at base and throughout is much less slender. 
The corolla averages somewhat shorter, too, usually measuring , 
trifle less than 2 cm. long, while the corolla of true P. canadensis 
is generally quite 2 cm. in length or even longer. Finally the leaves 
of the western plant are always of a linear-oblong type, & tyPe si 
frequently exhibited by true P. canadensis, at least the e™ 
leaves of which are generally more or less ovate-lanceolate. ; 
secondary toothing too of the typical form is usually deeper ap 



