MOSSES. 189 



tiiberance in the axils, or at the base of the leaves ; no appear- 

 ance of flowers in these plants is ever j^resented. 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 tirst 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 iiwolucrum (or iiidusium). 



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 fern^ 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 

 trunh. Some of the ferns are nsed medicinally ; the sirup, 

 called capillaire^ is prepared from the Adiantum cajpillas. 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 Equisetum hye- 

 male is know^n to housekeepers under the name of scouring- 

 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 flow^er 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, a^ represents the theca ; 

 h the i?edicel.^ or stem \.c the sheath ; dXh.Q operculum., or lid, 

 which, before the theca is ripe, is covered by the calyptra ; e 

 the calyptra., or veil ; / the fringe., or teeth, which, when the 



Sensitive fern— Namber of species of ferns— Sconring-rush.— 286. Mossps 



