74 
EQUISETACE.E. 
the lower internodes. The sheaths at the stouter parts of the 
stem are fully half an inch in length, and the teeth are as much 
more : the former have about thirty-two deep and distinct striae, 
which are furnished with rows of siliceous particles at their ed- 
ges ; the spaces between the striae have broad shallow furrows. 
The teeth are slender, setiform, closely appressed to the stem, 
frequently adhering at the summit in twos and threes, and fur- 
nished with dilated, semi-membranous, somewhat ragged edges 
at the base. The sheaths are pale green, with a distinct black- 
ish ring at the summit ; the teeth are black, with the membra- 
nous edges brown, and, in the lower sheaths, often clothed with 
a brown, byssoid pubescence. Each of the joints, with the ex- 
ception of five forming a slender apiculus at the summit, and 
six nearest the ground, is furnished at the base of its accompa- 
nying sheath with a whorl of slender branches : those of the 
lower sheaths are short and recurved, while those near the sum- 
mit are nine inches in length, and nearly erect : the varied di- 
rection of the branches is shown at fig. a. The number of 
branches in a whorl is very various : the respective numbers, 
counting from the summit, are these — five, six, seven, eight, nine, 
ten, thirteen, fourteen, fifteen, sixteen, eighteen, twenty, twenty- 
five, twenty-nine, thirty-three, repeated eleven times, thirty, 
twenty-eight, and sixteen, making a total of six hundred and 
seventy-eight. The colour of the branches is a delicate green, 
so beautiful as to attract the eye at a considerable distance. 
Each of these branches is composed of about eight or nine 
longish joints, and each joint terminates in a loose sheath : the 
branches have either eight or ten ribs, united in pairs, and rough 
with siliceous particles : the sheaths terminate in four or five 
teeth, each furnished at the extremity with a slender black bris- 
tle : a pair of ribs ascends into each of the teeth, and each rib 
is furnished, near its termination, with a series of rather long 
siliceous points, which give it a pectinated appearance. Such 
may be received as the description of a stem of normal size and 
characters, and the variations are very unimportant, chiefly con- 
sisting in size and number of branches, but rarely interfering 
with the figure of the frond, unless caused by circumstances, 
as excess of wet or drought, both apparently uncongenial to its 
