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Class Diccia.

Fig. 125.

The class Diæcia (two houses), has staminate and pistillate flowers on separate plants. The distinction with regard to the orders, as in the preceding class, is derived from the number of stamens.

There are no plants of the first order.

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Diandria. The 2d Order contains the willow (Salix), which has long and slender aments, both of staminate and pistillate flowers, the two kinds being on separate trees.

The order TRIANDRIA contains the fig (Ficus), remarkable for containing the flower within the fruit, which is botanically considered as a juicy receptacle, within which are concealed the minute flowers and seeds. The fig is peculiar to warm countries.

TETRANDRIA contains a parasite plant, the Misletoe ; but one species is indigenous to this country. The Druids* considered this plant as sacred to the sylvan deities. Tradition relates, that, where Druidism prevailed, the houses were decked with this plant, that the sylvan spirits might repair to them.

The order PENTANDRIA contains the hemp, hop, &c. Fig. 125, represents the pistillate and staminate flowers of the hemp (Cannabis sativa); at a, is the barren or staminate flower, oontaining five stamens, and having its calyx deeply five parted; the corolla is wanting. At b, is a fertile or pistillate flower with its calyx opening laterally ; C, shows the same flower divested of its calyx ; the seed is a nut, which is crowned with two styles. The hemp belongs to a family called Urtices (from Urtica a nettle); the fibres of its stems are manufactured into cloth, cordage and thread. The hop produces its fertile flowers in large cones formed of membranous, imbrica

* The Druids, it is supposed, derived their name from drus, a Greek word signifying oak, as it was in groves of this tree that the priests celebrated their mysterious rites, and sacrificed human victims to their sanguinary deities.

Class Dioscia-Willow-Misletoe-Hemp-Hop.

ted scales; these flowers have a peculiar odour, which is said to produce a narcotic effect upon the brain. The use of the flowers of the hop in beer are well known. This plant contains a small portion of the nitrate of potash (saltpetre).

HEXANDRIA, contains the honey-locust and green briar.

OCTANDRIA, has the poplar, (Populus), similar in natural character to the willow. Several intermediate orders occur before we arrive at the 15th order MONADELPHIA ; here we find the red cedar and the yew, which belong to the cone bearing family, with the pine and cypress. We have now

completed our remarks upon two classes which have imperfect flowers. Our review of these has been brief, when compared to the many interesting facts which presented themselves in association, with the various important plants which we have passed in rapid succession; but this very mass of matter has compelled us to dwell less upon particular facts. We have now but one more class to investigate, in order to complete our view of the Linnæan system.

LECTURE XXXVIII.

CLASS XXI.-CRYPTOGAMIA.

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THE twenty preceding classes in. clude the Phenogamous plants; we are now to consider the Cryptogamous class; we here find the stamens and pistils either wholly concealed from observation, or manifest only upon the strictest scrutiny. These plants constitute the first class of Jussieu, called acotyledonous ; their seed being desti

tute of any cotyledon. As we enter upon this last of the Linnæan classes, we shall find all our former principles of arrangement to fail us, and it might almost seem as if we had entered upon a new science. The class Cryptogamia includes all plants which do not find a place in some of the other classes.

Ferns, mosses, lichens and mushrooms constitute the princi. pal part of this class. At Fig. 126, a, is a fern, of the genus

Asplenium, which bears its fruit on the back of the leaves or fronds; at b, is a moss of the genus Hypnum, showing two of its flowers borne on slender pedicels or stems; at c, is a genus of the Lichen family ; at d, is the Agaricus, one of the most common of the mushrooms.

Some writer has said, that Linnæus, having arranged the plants which would admit of classification, took the remainder and cast them all into a heap together, which he called Cryptogamous; he did not, however, rest satisfied in thus throwing together the refuse of the vegetable world ; but subdivided this miscellaneous collection into orders; or we might more properly say, that he gave names to those divisions already marked out by nature.

Of these orders, which are natural families brought together on account of general resemblances and analogies, without re. ference to any one principle, there are six.

Filices, or FERNS. The 1st order contains the Ferns; their plume-like leaves are called fronds. The fruit, mostly disposed in dots or lines, grows on the back, summit, or near the base of the leaf or frond. You may here see (Fig. 127) a delineation of some of

Fig. 127.

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the various modes in which the fructification of ferns appears ; (a) genus POLYPODIUM or polypody, with capsules in roundish spots on the back of the frond ; (6) ASPLENIUM, capsules in lines nearly parallel, diverging from the centre of the frond ;

Orders marked out by nature-Ferns--Modes of the fructification of ferns.

(c) BLECHNUM, capsules in uninterrupted lines running parallel to the midrib of the frond on both sides; (d) PTERIS or brake, capsules forming lines on the edge of the leaf.

Some ferns bear their fruit in a peculiar appendage, as a spike or protuberance in the axils, or at the base of the leaves ; no appearance of flowers is ever presented. When the brown or white dust-like spots are examined with a microscope, they are found to consist of clusters of very small capsules, at first entire, but afterwards bursting elastically and irregularly. Besides attention to the situation and form of the capsules, it is necessary to observe the membrane which envelopes them; this is called their involucrum. The seed is as minute as the finest powder, and so light as to be wafted by the air to any distance or height; we thus often see ferns growing high on the trunks of trees, or on the summits of old buildings. Some ferns grow to a great height in southern latitudes, almost like trees. At the southern extremity of Van Diemen's Land, a species has been found, whose trunks attained to the height of twelve or sixteen feet. One species in our country,

ONOCLEA sensibilis, called the sensitive fern, is said to wither on being touched by the human hand, though the touch of other substances does not produce any similar appearances.

The number of species of ferns which are already known, amounts to about seven hundred. They generally abound in moist and shady situations, but are sometimes found on rocks and dry places and on the trunks and branches of old trees. 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 hyemale is known to housekeepers under the name of scouring rushes. The quantity of silex contained in the cuticle renders it a good substitute for scouring sand.

Musci, or MOSSES. The 2nd order contains the mosses, which are little herbs with distinct leaves, and often a distinct stem ; their conical, membranous corolla is called a calyptra or veil, its summit being the stigma; this veil clothes the capsules, which, before the seed ripens, is elevated on a fruit stalk. The capsule 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, which serves as a distinction in the order, The bar. ren flower of mosses consists of a number of nearly cylindrical, almost sessile anthers ; the fertile flowers of one pistil, seldom more, accompanied by several barren pistils. Both stamens

Sensitive fern-Number of species-Where they generally abound-Scpus: ing rushes-Masses.

and pistils are intermixed with numerous succulent threads. You may here observe (Fig. 128) the different parts of mosses ;

Fig. 128.

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a, represents the capsule; b, the pedicel or stem ; e, the sheath, which, before the pedicel grew up, served as a kind of calyx, to protect the embryo fruit; d, the operculum or lid, which, before the capsule is ripe, is covered by the calyptra ; e, the calyptra, or veil; f, the fringe or teeth, which, when the capsule is ripe, and has thrown off its other parts, often appear around its edge; g, the barren or staminate flower of a moss.

The mosses are generally perennial and evergreen, and capable of growing in colder climates than most other vegetables. In Spitzbergen, the rocks which rise from the surrounding ice, are thickly clothed with moss. A botanist who tra. velled in Greenland, counted more than twenty different species without rising from a rock where he was seated.

The parts of the mosses which have been described are not seen without the assistance of a good microscope. It is not to be expected that young botanists will be fond of this department of the science, although those who become acquainted with it, discover much enthusiasm in its pursuit. The following interesting remarks on Cryptogamous plants are taken from an English writer.

“ Mosses and Ferns, by the inconsiderate mind, are deemed an useless or insignificant part of the creation. That they are not, is evident from this, that He who made them has formed nothing in vain, but on the contrary has pronounced all his creation to be good. Many of their uses we know ; that they have many more which we know not, is unquestionable, since there is probably no one thing in the universe, of which we can dare to assert, that we know all its uses. Thus much we are certain of, with respect to mosses, that as they flourish

Explain Fig. 128—Mosses capable of enduring cold--Microscope necessary in examining mosses-Remarks of an English writer.

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