Part 12 (2/2)

The plant sends up branches of two kinds froth of a72, _C_) is distinctly jointed, bearing at each joint a toothed sheath, best seen in the younger portions, as they are apt to be destroyed in the older parts Sometimes attached to this are small tubers (_o_) which are ive rise to new stems They have a hard, brown rind, and are composed within mainly of a firm, white tissue, filled with starch

The surface of the stem is marked with furrows, and a section across it shows that corresponding to these are as e air spaces that traverse the stem from joint to joint From the joints numerous roots, quite like those of the ferns, arise

If the ste up in the late fall or winter, nu froround into branches of two sorts Those produced first (Fig 72, _A_), in April or May, are stouter than the others, and nearly destitute of chlorophyll They are usually twenty to thirty centiht reddish brown color, and, like all the stems, distinctly jointed The sheaths about the joints (_L_) are er than in the others, and have froe black teeth at the top These sheaths are the leaves At the top of the branch the joints are very close together, and the leaves of different form, and closely set so as to form a compact cone (_x_)

A cross-section of the steround steer, and in addition there is a large central cavity The fibro-vascular bundles (_fb_) are arranged in a circle, alternating with the air channels, and each one has running through it a se

The cone at the top of the branch is made up of closely set, shi+eld-shaped leaves, which are mostly six-sided, on account of the pressure These leaves (_F_, _G_) have short stalks, and are arranged in circles about the ste down fro by a cleft on the inner side (_G_, _sp_) They are filled with a htest jar when ripe

The sterile branches (_B_) areones, and the sheaths shorter Surrounding the joints, apparently just below the sheaths, but really breaking through their bases, are circles of slender branches rese the row to a height of forty to fifty centimetres, and from their bushy form the popular name of the plant, ”horse-tail,” is taken The surface of the plant is hard and rough, due to the presence of great quantities of flint in the epidermis,--a peculiarity common to all the species

The ste smaller as they approach the epiderreen branches contain chlorophyll, and the walls of some of them are thickened The fibro-vascular bundles differ entirely froular in section (_E_), with the point inward, and the inner end occupied by a large air space The tracheary tissue is only slightly developed, being represented by a few vessels[9] (_tr_) at the outer angles of the bundle, and one or two smaller ones close to the air channel The rest of the bundle is made up of nearly uniform, rather thin-walled, colorless cells, soer, and have perforated cross-walls, representing the sieve tubes of the fern bundle There is no individual bundle sheath, but the whole circle of bundles has a common outer sheath

[9] A vessel differs fro composed of several cells placed end to end, the partitions being wholly or partially absorbed, so as to throw the cells into close coated cells whose walls present a peculiar beaded appearance, due to the deposition of flint within theed in vertical lines, and reseh differing in souard cells have heavy deposits of flint, which here are in the form of thick transverse bars

The spore cases have thin walls whose cells, shortly before s upon their walls, which have to do with the opening of the spore case The spores (_H_, _I_) are round cells containing es called elaters The elaters are extrehtly when ain when dry (_H_) By dusting a few dry spores upon a slide, and putting it under the microscope without any water, theupon them will cause the elaters to contract, but in a moment, as soon as the moisture of the breath has evaporated, they will uncoil with a quick jerk, causing the spores to eres, which closely rese the spores in water With care it is possible to get the mature prothallia, which should be treated as described for the fern prothallia Under favorable conditions, the first antheridia are ripe in about five weeks; the archegonia, which are borne on separate plants, a feeeks later The antheridia (Fig 72, _J_, _an_) are larger than those of the ferns, and the spermatozoids (_K_) are thicker and with fewer coils, but otherwise onia have a shorter neck than those of the ferns, and the neck is straight

Both ular in shape

There are a number of common species of _Equisetu rush (_E hiemale_), are unbranched, and the spores borne at the top of ordinary green branches; others have all the ste like the sterile ste cone at the top of some of them

CLass III--THE CLUB MOSSES (_Lycopodinae_)

The last class of the pteridophytes includes the ground pines, clubcultivated plants nuinella_)

Two orders are generally recognized, although there is some doubt as to the relationshi+p of the er club mosses (_Lycopodiaceae_) is represented in the northern states by a single genus (_Lycopodiu 73) is a fareen forests of the northern United States as well as in the er northern cities is often sold in large quantities at the holidays for decorating It sends up fro, woody, subterranean stem, numerous smaller stems which branch extensively, and are thickly set with s much like a little tree At the ends of some of the branches are s, scale-like leaves, much as in a fir cone Near the base, on the inner surface of each of these scales, is a kidney-shaped capsule (_C_, _sp_) opening by a cleft along the upper edge and filled with a mass of fine yelloder These capsules are the spore cases

The bases of the upright steher up The leaves are in shape like those of aleaves are broader and when slightly in

The stem is traversed by a central fibro-vascular cylinder that separates easily fro to the rupture of the cells of the bundle sheath, this being particularly frequent in dried specie 73, _E_) Within the epiderround tissue of fir the central oval or circular fibro-vascular cylinder This shows a number of white bars (xylenifying the section round tissue (_G_) are seen to be oval in outline, with thick striated walls and situdinal sections they are long and pointed, belonging to the class of cells known as ”fibres”

[Illustration: FIG 73--_A_, a club moss (_Lycopodiule scale with sporangium (_sp_) _D_, spores: i, from above; ii, from below, 325 _E_, cross section of stem, 8 _fb_ fibro-vascular bundle _F_, portion of the fibro-vascular bundle, 150 _G_, cells of the ground tissue, 150]

The xylem (_F_, _xy_) of the fibro-vascular bundle is composed of tracheids, much like those of the ferns; the phloem is composed of narrow cells, pretty much all alike

The spores (_D_) are destitute of chlorophyll and have upon the outside a network of ridges, except on one side where three straight lines converge, the spore being slightly flattened between the is known of the prothallia of our native species