46 
EQUISETACE/E. 
eight in number, the granulations of the ridges between them 
feel slightly rough to the nail if drawn along them. The stem 
is divided into eleven compartments by means of transverse 
septa ; the internodes are an inch and a quarter or an inch and 
a half in length : the sheaths occur at the septa, and correspond 
in number ; they considerably exceed the stem in circumference, 
and in consequence are loose : the ridges of the stem enter the 
sheaths, and each then divides into two parallel portions, and 
terminates in one of the teeth, which are eight in number, 
acute, wedge-shaped, tipped with black, and furnished with 
nearly transparent membranous edges. There are nine whorls 
of branches : these rise from the furrows of the stem, close to 
the base of the sheaths ; they never exceed the furrows in num- 
ber, and are frequently fewer; the short sheath at the base of 
each is black, and these form a series of black rings round the 
stem : they are divided into six or eight joints, of which the 
basal and apical are the shortest : they are generally live-ribbed, 
and the sheaths occurring at the joints are five-toothed, each 
tooth receiving one rib, which is always divided before its termi- 
nation, and the divisions do not ascend to the extreme apex of 
the tooth ; the teeth are tipped with brown, and are furnished 
with semi-hyaline marginal membranes : the branches vary 
greatly in length. 
The catkin is long and rather narrow ; when mature it stands 
on a distinct stalk of its own length : it is terminal, and after 
discharging its seeds it appears to perish, the stem and branches 
continuing to retain their vigour. There is no apiculus, the 
extreme summit being composed of a scale similar to the rest : 
at first the scales are crowded together, forming a black mass, 
they afterwards separate, the peduncle supporting each becomes 
visible, and the catkin, increasing in length, assumes a brown 
colour. The catkin appears in May and June. 
This species is subject to extraordinary variations, three of 
which have received distinguishing names. 
The first of these appears to be universally known by the 
name of polystachion : it is at once distinguished by its nume- 
rous catkins : these are usually and principally borne on the two 
upper whorls of branches ; the main stem generally terminating 
