REVIEWS. 241 
ter of the order and of the genus is the same. Of this genus or 
order there are eight or nine British species, and possibly about 
an equal number of exotic or foreign species: they are all dis- 
tinguished by their hollow-jointed, round, angular stems, with 
sharply toothed sheaths, often with slender spreading branches, 
which spring from a joint, and encircle the stem by their bases. 
The fruit is in terminal, ovate or cylindrical spikes, either pro- 
duced on the branched stem or on a separate or distinct, un- 
branched stem, which however arises from the same root as the 
barren stem does. In the position of their branches, and in their 
general outline or port, the species of this order have a slight 
resemblance to a Pine or Fir. They are all perennial or of long 
duration, and grow mostly im cool, shaded, moist places. The 
Field Horse-tail grows in fields, and is accounted an agricultural 
weed, and one not easily extirpated, its roots spreading widely 
and penetrating deeply into the soil. The Club Mosses, Lycopo- 
diacee, consist of only one genus, like the last-mentioned, but 
they differ widely from the Horse-tails im habit, general aspect, 
structure, and localities (places where they grow). ‘They have a 
greater resemblance to Mosses (Musci) than to Ferns. They are 
leafy plants, with branched, trailing, wiry stems (few are erect) ; 
their substance is dry and rigid; and their fructification (mat- 
ter by which they are reproduced) is produced in terminal, dense, 
cylindrical spikes. They are all perennial, and grow mostly on 
open mountaious heaths, on exposed moors, and in similar 
places. Several foreign species grow luxuriantly under the shel- 
ter and drip of trees. They are all objects of great beauty and 
interest, and have in recent years been rather extensively culti- 
vated, especially under -glass, with Ferns and other suitable 
plants. The aquatic plant Quillwort has only very recently been 
associated with the Club Mosses, to which indeed it has but a 
very feeble affinity; it grows under water in alpine lakes, and 
is, like the others, a perennial. Péludaria (Pillwort) belongs to 
the order Marsileacee, and is the only British example of this 
genus and order. The stems are thread-like, quite prostrate, 
with tufts of greenish, narrow, pointed, erect leaves above, and 
several small, slender roots below. The fruit is in round, black- 
ish bodies, about as large as peppercorns, solitary, and opposite 
to the rootlets of the creeping stems. They grow in watery 
places, and are rather rare. The Charas (Characee) are all 
N.S. VOL. I. 21 
