t3 
12 Rhodora [JANUARY 
large number examined show some intergradation. —Intergrading 
forms have been observed growing together at Lexington, Ky. 
The principal distinguishing characters of the three forms are 
pointed out in the following descriptions: 
Lactuca virosa has oblong-obovate obtuse leaves, rather thin and 
weak in texture and inclined to be bullate. So far as can be deter- 
mined in pressed specimens they are horizontal. The achenes are 
black or very dark, with a comparatively short stout beak. 
The leaves of Z. scariola are runcinate, or pinnately lobed, firm in 
texture and with or without spines on the back of the midrib. They 
are turned in a vertical plane. The flowers are smaller than those 
of Z. virosa and the achenes, also smaller and more slender, are 
light brownish-gray, usually mottled and with long slender beaks. 
The leaves of Z. scariola integrata have nearly parallel margins, 
with usually a broadly deltoid acute apex, and a firm texture. They 
are turned in a vertical plane and the midrib is either with or without 
spines. The flowers and achenes do not appear to differ from those 
of the species. 
The flowers of both the species and the variety are yellow, but in 
the dried herbarium specimen they change to blue. 
WASHINGTON, D. C. 
LEDUM PALUSTRE, Var. DILATATUM ON Mr. KaTtaHDIN. — While 
examining with Professor E. B. Delabarre some Labrador material of 
Ledum palustre, L., and its var. dilatatum, Wahl., I was surprised to 
find in the Gray Herbarium a beautifully fruited specimen of the 
characteristic var. dilatatum collected by the late George Thurber on 
the summit of Mt. Katahdin, Maine, in August, 1847. The Thurber 
sheet is labeled “woods & summit of Katahdin, Me.", and contains 
two branches; one, a loosely forking branch of typical fruiting Z. 
groenlandicum, apparently from * woods," the other, a dwarfed and 
small-leaved branch of heavily fruited Z. palustre, var. dilatatum, 
obviously from the “ summit.” 
Ledum palustre of Arctic regions presents two strongly marked 
variations, the true Z. palustre with narrowly linear rigid leaves 1 to 
3 cm. long, and the var. dilatatum with leaves linear-oblong as in 
L. groenlandicum. From the latter species of Greenland and boreal 
America, which commonly has 5 to 7 stamens and narrowly oblong or 
