170 EQUISETACEA: 
hollow angular channelled branches, which are in most cases whorled around © 
them. The different species are not, however, always very readily discrimi- 
nated, several of these being very similar, and the structure of the sheaths 
around the joints, and the ridges on the surface of the stems, often form the 
chief features of their distinction. 
The Cornfield Horsetail is not, like most of the species, peculiar to marshy 
soils, but springs up everywhere, and is not only an annoyance to the farmer, 
who finds it difficult of eradication from his corn or pasture lands, but is 
also often a troublesome intruder into the garden. Most of us have amused 
ourselves in childhood by giving a sudden pull to the stem or branch, and 
thus separating it into small portions, leaving the sheath in which each 
portion was enveloped disclosed to view, and needing no microscope by 
which to discover its little sharp membranous teeth. This species has a 
long creeping root-stem, which is hollow, very much branched, and jointed 
like the stem which rises above the ground ; and it throws out at each joint 
a whorl of tough fibrous roots. It has two kinds of fronds, the one fertile, 
and without branches ; the other barren, and surrounded by the green whorls 
of rigid branches. 
The fertile stem rises above ground in March, and is matured by April or 
May, at which season the barren stems may often be seen, lately emerged 
from the earth, arrayed in the most delicate green colour, and very brittle. 
When the fertile stem has attained maturity, it is, when growing on soils 
suitable to it, about eight or ten inches high, but it is more frequently about 
half that height. It is hollow, succulent, pale brown, without furrows, and 
divided at intervals into joints; the length of the spaces between the joints 
is very variable, the joints at the lower part of the stem being usually closer 
together than at the upper. The sheaths are yellowish at the base, and have 
about ten dark-brown or black slender teeth, with very sharp points. The 
upper sheaths are longer than the lower ones, and the black teeth are often 
tipped with white, and have a clear white margin. 
The cone-like fructification is at the top of the stem, and is about an inch 
long, tapering upwards, terminating in a blunt point, and standing on a 
distinct foot-stalk about half its length. It is of a pale, or sometimes of 
a reddish-brown colour. The capsules are attached to round scales, and 
arranged in whorls around them. The number of scales varies, but they are 
not so numerous in this species as in some others. In May, when the catkin 
is matured, and sheds its numerous fine green spores, these, like the spores 
of other species, are, by the aid of the microscope, seen to be surrounded by 
delicate threads, which uncoil with such curious movements, that when 
looking at them we can scarcely persuade ourselves that the motion is purely 
mechanical, and is not the result of animal life. The oblong capsules, when 
ripe, open by two valves, and discharge their powder-like spores or seeds. 
The barren frond of this Equisetum is avery different-looking plant, and 
is handsomer than the fertile one. When first it rises, it seems merely a 
hollow pointed stem, for its branches are not then seen. It is, however, 
when fully grown, two or two and a half feet high, and has whorls of long, 
green, rigid, and four-angled branches, either half-way down, or throughout 
its whole length, and two or more fronds rising from the same part of the 
