EQUISETACEA—_HORSETAILS 169 
The capsules containing the spores are placed on short stalks just at the 
base of the leaves, in the angle formed by the leaf and stem. They are 
about the size of a peppercorn, and closely covered with jointed hairs of a 
light-brown colour. They consist of four cells, and, when quite ripe, split 
open from the upper part into quarters, which still remain on the little stalk. 
The spores are placed along the centre of the valves, forming four rows ; and 
the lower part is occupied by granular bodies, and the upper by pollen-like 
powder. The larger grains are the macrospores, and the smaller microspores. 
The macrospore develops into a prothallus upon which arises an arche- 
gonium, which is fertilized by the contents of the microspore. 
Order CV. EQUISETACEZ:—HORSETAILS. 
These are leafless, flowerless, sometimes aquatic plants, with a hollow 
subterranean, creeping stem, and erect hollow fronds marked with lines, and 
sheathed at the bases of the joints. The fructification is produced in terminal 
spikes or catkins, either placed on the stem of the branched frond, or on a 
separate simple frond of earlier growth. 
HorseEtalL (Equisétum).—Stems jointed and tubular, fertile ones mostly 
unbranched and succulent ; barren stems with whorled branches ; fructifica- 
tion in a catkin. Name from equus, a horse, and seta, a hair, because some of 
the barren fronds resemble the tail of a horse. 
HORSETAIL (Equisetum). 
1. Cornfield Horsetail (£. arvénse).—Barren stems, with few furrows, 
slightly rough; branches rough, with three or four simple angles; fertile stem 
unbranched, with few loose distant sheaths. This is by far the commonest 
of our native Horsetails, some of which are known to all who observe the 
plants which grow wild. These plants are commonly called Jointed Ferns, 
or Leafless Ferns, though they have not a very obyious affinity with the 
leafy species commonly recognised as ferns. hey are destitute of any 
green expansions ; they are jointed at regular intervals, the joints or knots 
being solid, and surrounded by membranaceous toothed sheaths, while the 
portions between the joints are hollow. Their branches are rigid and 
whorled, and the fructification placed in cone-like heads made of scales, to 
the lower face of which the spore-cases are attached in a row round the 
margin. 
The stem is chiefly composed of cellular matter, but towards the outer 
portion there is a layer of woody fibre. The cuticle, or thin skin, which 
covers the Horsetails, is in all the species regularly and beautifully coated 
with particles of flint, arranged in lines and other forms, often not the five 
hundredth part of an inch in diameter. These particles were discovered by 
Sir D. Brewster to lie, in the greater number of cases, in simple straight 
lines ; but others are grouped into oval forms like the beads of a necklace, 
and connected together by a minute chain of particles. 
The Horsetails are readily distinguished by their leafless stems and the 
Iv.—22 
