CHARACTERS OF BRITISH PLANTS. 75 
Carduus pratensiis (Huds.) and C. Forsteri (Bab.)—The 
suckers or “ creeping root” of the former readily distinguish 
it from the latter, in which the stems proceed from the 
centre of the tufted root year after year. The stem-leaves 
of C. pratensis are occasionally as much “ pinnatifid” and 
prickly as those of C. Forsteri. 'The heads of the latter are 
not always two or three together. 
Erythrea Centaurium (Pers.) and E. pulchella (Hook.)— 
These look the most distinct among our four alleged British 
species. Occasionally, however, among plants of E. Cen- 
taurium I find solitary individuals which assume the habit of 
E. pulchella, and in which the calyx is either equal to the 
tube of the opened corolla, or considerably shorter, even on 
the same single plant. In these specimens the leading shoot 
has probably been injured by cattle or insects at an early 
stage of growth. 
Erica Tetralix (Linn.) and E. Mackaii (Hook.)—Itis diffi- 
cult to find characters which will keep these distinct in 
description. The included or protruded style, as I have 
before observed, is a condition of age, and shared by both. 
In one or two of my specimens of E. Mackaii the leaves are 
so revolute at the margin as to be quite linear; while I have 
seen many plants of E. Tetralix, in which the leaves were 
more broadly ovate than in the broadest leaved specimens 
of E. Mackaii. The glabrous upper surface of the leaves 
and midrib beneath occur in both. The sepals of E. Mackaii 
are not invariably glabrous. I have not yet found either 
sepals or germen glabrous in E. Tetraliz. If these are not 
distinct species, the connecting links must be sought in the 
localities of .E. Mackaii, which is the variation from the 
typical form of E. Tetraliz, and which may consequently be 
expected to shade off into the true type. 
Erica ciliaris (Linn.) var. Watsoni.—This is the name 
given in Decandolle’s Prodromus to the hybrid plant from 
Truro, mentioned in page 208 of the British Flora. 1 
- Should rather unite it with E. Tetraliz, as having more the 
a2 as 
