equisetum. 271 
whorls; in very luxuriant plants, the branches are now 
and then themselves branched upon a similar plan. 
Like the other species, this has a branching under¬ 
ground creeping stem, which is black, and produces whorls 
of branched fibrous roots from its joints. The above¬ 
ground stems are slender, and erect in their mode of 
growth ; from two to three or four feet high ; deeply fur¬ 
rowed, with a double row of elevated points along the 
ridges, which are usually from eight to twelve, but some¬ 
times fourteen in number. The sheaths are close, cylin¬ 
drical, and striated like the stem, terminating in a number 
of teeth equalling the striae ; these teeth are long, slender, 
awl-shaped, black with pale membranous margins, and 
usually, but not always, persistent. The sheaths are, for 
the most part, entirely black, but here and there they 
occur with a narrow greyish ring, variable in position, 
being sometimes central, and at other times near the base 
or near the margin ; it is, however, we believe always, much 
less decided and clearly defined than the pale-coloured 
band on the sheaths of E. hyemale. 
The section of the stem differs from that of E. hyemale, 
to which it presents a general resemblance, in being 
smaller, showing fewer ridges, and having the cavities 
