MOSSES. 
189 
tuberance in tlie axils, or at the base of tbe leaves ; no appear- 
ance of flowers in these plants is ever presented. When the 
brown or white dust-like spots {sori) are examined with a 
microscope, they are found to consist of clusters of very small 
spore-cases, at first entire, but afterward bursting elastically 
and irregularly. Besides attention to the situation and form 
of the sporangia, it is necessary to observe the membrane which 
envelops them ; this is called their involiicrum (or indusium). 
The spores are minute as the finest powder, and so light as 
to be wafted by the air to any distance or hight. Some ferns 
grow to a great hight in southern latitudes, almost like trees. 
One species, Onoclea sensihilis, the sensitive fem^ is said to 
wither on being touched by the hand, though the touch of other 
substances does not produce the same phenomenon. The stem 
of the fern is a rhizome, which creeps along under the surface 
of the ground, sending off roots and leaves, or an mrogenous 
trunk. Some of the ferns are used medicinally ; the sirup, 
called cajpillaire^ is prepared from the Adiantum Camillas. A 
species of Aspidium is covered with a woolly substance, and 
is hence called the Tartarian lamb. The number of species of 
ferns which are already known, amounts to about two thousand, 
the number of genera to one hundred and eighty-three. Ferns 
abound in moist and shady situations ; they are sometimes found 
on rocks and dry places, on the trunks and branches of trees, or 
on the summits of old buildings. The frond, or leaf of the 
fern, is often pinnate^ or divided like a feather ; sometimes it 
is undivided, and resembles a palm-leaf. The Eqtjisetum hye- 
male is known to housekeepers under the name of scowing- 
rush. The quantity of silex contained in the cuticle renders it 
a good substitute for scouring-sand. 
286. Order Musci — contains the mosses^ which are little herbs 
with distinct stems ; their conical, membraneous corolla is called 
a calyptra^ or veil ; this veil clothes the capsules, which, before 
the seeds [sporules) ripen, is elevated on a foot-stalk. The cap- 
sule, called theca^ is of one cell, and one valve, opening by a 
vertical lid ; the seeds are very numerous and minute. In some 
genera the veil is wanting ; this serves as a distinction in the or- 
der Musci. The barren flower of mosses consists of a number 
of nearly cylindrical, almost sessile anthers ; the fertile flowers 
have one perfect pistil, seldom more, accompanied by several 
barren pistils. Both stamens and pistils are intermixed with 
numerous succulent threads. Fig. 160, represents the tlieca ; 
h the pedicel.^ or stem ; c the sheath / d the operculum.^ or lid, 
which, before the theca is ripe, is covered by the calyptra ; a 
the calyptra^ or veil ; f the fringe^ or teeth, which, when the 
Sensitive fern -Number of species of ferns— Scouring-rush.— 286. Mossps 
