Fern.

The Ferns are a very numerous order of acrogenous plants, growing in the temperate regions from a rhizome or underground stalk (commonly called its root), which throws up "fronds" or leaves with a strong midrib; this midrib is commonly called its stalk, but in tropical countries the fern stalk rises above ground to the height of 30 or 40 feet, and then it is seen that the ordinary stalks are but the midribs of the fronds. There are between two and three thousand species of fern. The fronds open in a peculiar manner, unwinding as it were from a round ball. The "sorri" or seed-cases are situated at the back of the fronds in little brown spots, each of which is found to consist of a heap or collection of round capsules, and if these be placed under the microscope they have the appearance of little membraneous cases covered with net-like markings, and at the upper part a striated band of a brown colour, which after a time stretches out into a nearly straight line, tearing open the bag or capsule, and a number of seeds escape. Ferns grow best in damp and shady situations, and will thrive well in damp mould under a glass case.

6. Marchantiaceæ (Liver-worts).

Liver-worts.

These Liver-worts are much like Lichens, growing between and uponstones near springs and moist places, and forming a broad thallusor root from which grow cup-shaped sporangia or seed-cases. TheMarchanta polymorpha is one of its chief members.

7. Jungermanniaceæ (Scale-mosses).

Scale-moss.

The Scale-mosses grow in moist places and under the stems of trees andplants. Their appearance is scaly, and they have a sort of stalk.

8. Bryaceæ (Urn-mosses).

Urn-moss.

Urn-mosses comprise the most ordinary of the mosses, the "Brium,"which grows on the ground everywhere, forming tufts; itsfructification resembles an urn, and hence its name.

9. Lycopodiaceæ (Club-mosses).

Club-moss.

These are very beautiful mosses, of a bright green colour, growing inmoist places. There are about 200 species of club-mosses known. Thecommon Lycopodium is its most characteristic member. It grows wellwith ferns under a glass case.

10. Equisetaceæ (Horsetails).

Horsetail.

The Equisetaceæ are the highest of the Acrogens, and nearly resemblethe Endogens; they grow in ditches and pools, have a hollow stemwith joints at regular intervals from each of which a whorl of greenmodified leaves arises; they are very full of earthy matter (silica),and one kind (Equisetum Hyemale), called Dutch Rush, is so roughwith it that it is used for polishing and scraping many articles.

The second division of the vegetable kingdom are the Endogenæ, which are those plants growing from a central bud only, as the palms, bamboos, and canes of all kinds, the grasses and all graminiferous or grain-bearing plants, as wheat, barley, &c. They have but one cotyledon in the seed and have no bark, but in place thereof a kind of natural varnish or thin coating of silica; this varnish or external polish is seen in the stalks of corn and on canes. Their leaves are often of great size, the veins run parallel to each other (fig. 8), they often grow from an expanded base which surrounds the stalk as in corn, and branch off at regular intervals making knobs or joints, as may be seen in the bamboo cane (figs. 9 and 10), in other cases they branch off spirally, and when fallen form a sort of trellis-work on the stem (as in some of the palms) but always in a regular manner. The wood of this family of vegetables has the same porous structure as cane (figs. 11, 12, 13,14), and is often hollow in the centre, becoming more and more solid according to the age of the tree. The stems of these plants are limited in growth and soon acquire their full size, which never exceeds eighteen or twenty inches in diameter although some of the palms are nearly 150 feet high. When the stem has acquired its full size, the continual production of more woody fibres makes it impossible that these (like the exogenæ) can have a very extended period of existence, for when every part of the stem is full of woody matter, the plant ceases to grow from obstruction to the circulation of the juices. The stems of some of this family are always hollow like the stalks of corn; this arrangement allows of great elevations without bending, and is found to be the form which gives the greatest strength from a given quantity of material—one of those beautiful mechanical perfections of nature which man first admired and then endeavoured to imitate.

FIG. 8.—ENDOGENOUS LEAF,
SHOWING PARALLEL VENATION.

FIG. 9.—BAMBOO CANE,
SHOWING JOINT.

FIG. 10.—BAMBOO CANE,
SPLIT OPEN.