1911] Fernald,— Variations of Lathyrus palustris 47 
THE VARIATIONS OF LATHYRUS PALUSTRIS IN EASTERN 
AMERICA. 
M. L. FERNALD. 
THE circumpolar Lathyrus palustris L. has long been very perplex- 
ing to the student of systematic and geographic botany. As repre- 
sented in many regions it occurs in two or more forms which by some 
authors have been treated as varieties, by others as distinct species. 
Torrey € Gray, for instance, recognized in Ámerica seven pronounced 
variations of L. palustris, besides L. myrtifolius Muhl. which was 
afterward treated, by Dr. Gray at least, as a variety of L. palustris. 
In eastern America there are three primary variations of L. palus- 
tris. One, a plant of comparatively coarse habit, varies from 5 
(rarely only 3)-12, averaging 7 dm. in height, has coarse glabrous 
ordinarily more or less winged stems, excluding the wings 1.5-3 
(averaging 1.8) mm. in diameter below the lowest peduncle; 2-5 
pairs of elliptic to broadly lanceolate or oblanceolate glabrous leaflets 
3-8.5 em. long, and 3-5 (rarely 8) large purple flowers 1.6-2.5 cm. 
long. This plant in its chief characters matches Old World material 
of L. palustris and is the form taken by Seringe, Reichenbach, Rouy & 
Foucaud, Ascherson & Graebner, and other critical students of the 
European flora as true L. palustris (var. genuinus Grenier & Godron; 
var. latifolius Lambertye). 
The second striking variation of L. pluie: is a much smaller plant 
with the low glabrous slightly winged or wingless stems 1-6 (rarely 8) 
dm., averaging 3.7 dm., high, and below the lowest peduncle only 
0.5-1.5 (average 0.9) mm. in diameter. This plant has ordinarily 
2 or 3 (rarely 4 or 5) pairs of linear or lanceolate glabrous leaflets, 
and its 2-5 flowers are about 1.5 cm. long. This, as shown by com- 
parison with Seringe’s material in the DeCandolle Herbarium at 
Geneva, is L. palustris, var. linearifolius Seringe (L. viciaeformis 
Wallr.). 
The third primary variation of L. palustris is var. myrtifolius 
(Muhl.) Gray, by some authors treated as a species, L. myrtifolius 
Muhl. In this extreme the stems are as slender as in var. lineari- 
folius and commonly wingless, but as tall as in typical L. palustris; 
the 2 or 3 pairs of elliptical to broadly lanceolate leaflets are mostly 
