WATEK EQUISETUM. 
55 
the creatures, and the noise made by their champing it we could 
distinctly hear in the evening at many yards’ distance.” 
The roots of the water Equisetum are numerous, black, fi- 
brous and sinuous : they spring from the bases of the submerged 
sheaths in a manner precisely similar to that of the branches, 
and those which originate near the surface of the water not un- 
frequently ascend for a time in the same way. The rhizoma is 
creeping, and extends horizontally in every direction, forming a 
matted mass in the mud of ponds and ditches where the plant 
occurs : it is of a brown colour, with jet black sheaths, which 
are rather more approximate than in ascending stems, but in 
other respects scarcely different. In winter, when the exposed 
portion of the stem of the preceding year is dead, the remain- 
ing portion becomes prostrate on the mud, still however re- 
taining some of its lower branches, which may be seen in the 
summer in a state of incipient development : these, together with 
others in a still younger state, form the ascending stems of the 
ensuing year. 
The engraving at page 51 represents a moderately sized stem 
of the water Equisetum, of its natural size and proportions : one 
much larger might have been selected, but its representation 
would have been more difficult. The stem is perfectly erect, and 
about twenty-five inches in height, of which seventeen inches were 
above water, and the remainder submerged. The submerged 
portion is smooth, the apical portion slightly striated, (the striae 
are much more distinct in immature and barren stems) : its ave- 
rage diameter is a quarter of an inch : it is divided by transverse 
septa into thirty compartments, thirteen of which were above, and 
the remainder below the surface of the water : the internodes 
above water vary from three quarters of an inch to an inch and 
three quarters in length ; those submerged are much more 
crowded. The sheaths are about a quarter of an inch in length ; 
they are green, concolorous with the stem, and of nearly equal 
diameter, so that they clasp it very tightly : the teeth are sixteen 
to twenty in number, sharp-pointed, always distinctly separated, 
black or dark brown, and not unfrequently furnished with a very 
slender, white, membranous edge. There are six whorls of 
ascending branches : these rise from the base of the sheaths from 
