Part 15 (1/2)

A cross-section of the steh it These are the fibro-vascular bundles which in the monocotyledons are of a simple type The bulb is composed of thick scales, which are thwise, we shall probably find the young bulb of next year (Fig _C_, _b_) already for as a bud at the base of the stem of the present year

The flower is made up of five circles of very much modified leaves, three leaves in each set The two outer circles are htly narrower and strongly tinged with red on the back, co the three inner ones before the flower expands The latter are pure yellow, except for a ridge along the back, and a few red specks near the base inside These six leaves constitute the perigone of the flower; the three outer are called sepals, the inner ones petals

The next two circles are co the pollen spores[12] These are the stamens, and taken collectively are known as the ”_Andrcium_” Each leaf or stamen consists of two distinct portions, a delicate stalk or ”fila part, the ”anther” (_an_) The anther in the freshly opened flower has a smooth, red surface; but shortly after, the flower opens, splits along each side, and discharges the pollen spores A section across the anther shows it to be coia or pollen sacs attached to a co _H_)

[12] The three outer stamens are shorter than the inner set

The central circle of leaves, the carpels (collectively the ”gynciu 81, _E_) This shows three distinct portions, the ovule-bearing portion below (_o_), the ”ovary,” a stalk above (_st_), the ”style,” and the receptive portion (_z_) at the top, the ”stigma and ovary show plainly their co divided into three lobes, the latter co flattened at the sides with a les The ovules, which are quite large, are arranged in ts in each chamber of the ovary, attached to the central column (”placenta”)

The flowers open for several days in succession, but only when the sun is shi+ning They are visited by numerous insects which carry the pollen froh the long style, finally reaches the ovules and fertilizes them Usually only a co almost always a number of irown about a month after the flower opens, and finally separates into three parts, and discharges the seeds These are quite large (Fig 81, _J_) and covered with a yellowish brown outer coat, and provided with a peculiar, whitish, spongy appendage attaching it to the placenta A longitudinal section of a ripe seed (_K_) shows the very sular embryo (_em_), while the rest of the cavity of the seed is filled with a white, starch-bearing tissue, the endosperm

[Illustration: FIG 82--_Erythroniule epidermal cell from the petal, 150

_C_, cross-section of a fibro-vascular bundle of the steitudinal section of the sas of the vessels, 150 _F_, a bit of the epider pores, 50 _G_, a single breathing pore, 200 _H_, cross-section of a leaf, 50

_st_ a breathing pore _m_, thepore, 200 _J_, young embryo, 150]

A microscopical examination of the tissues of the plant shows the especially the case with the fibro-vascular system

The epidermis of the leaf is readily re cells with large breathing pores in rows The breathing pores are er than any we have yet seen, and are of the type coiosperms The ordinary epidermal cells are quite destitute of chlorophyll, but the two cells (guard cells) enclosing the breathing pore contain nu nuclei of these cells are usually conspicuous (Fig 82, _G_) By placing a piece of the leaf between pieces of pith, and les to the longer axis of the leaf, so pores will probably be cut across, and their structure ure 82, _I_

The body of the leaf is ular shape and with large air spaces between (_H_, _ this tissue are fibro-vascular bundles of a type structure similar to that of the stem, which will be described presently

The stee cells with thin walls, which in cross-section show nuular, intercellular spaces (_i_) at the angles These cells contain, usually, more or less starch The fibro-vascular bundles (_C_) are nearly triangular in section, and resemble considerably those of the field horse-tail, but they are not penetrated by the air channel, found in the latter The xylem, as in the pine, is toward the outside of the stem, but the boundary between xyle no cambium present In the xyleuishable from the other cells by their definite foritudinal sections show spiral and ringed thickenings The rest of the xylem cells, as well as those of the phloeround tissue, except for their much smaller size, and absence of intercellular spaces

The structure of the leaves of the perigone is reen leaves, but the tissues are somewhat reduced The epider pores, but these are absent from their inner surface, and from both sides of the petals

The walls of the epidermal cells of the petals are peculiarly thickened by apparent infoldings of the wall (_B_), and these cells, as well as those below them, contain sht color of the flower is due The red specks on the base of the perigone leaves, as well as the red color of the back of the sepals, the stalk, and leaves are due to a purplish red cell sap filling the cells at these points

The filaments or stalks of the stamens are made up of very delicate colorless cells, and the centre is traversed by a single fibro-vascular bundle, which is continued up through the centre of the anther To study the latter, thin cross-sections should be ia, or pollen sacs, is surrounded on the outside by a wall, consisting of two layers of cells, becole fibro-vascular bundle is seen (Fig 81, _H_) On opening, the cavities of the adjacent sporangia are thrown together The inner cells of the wall are82, _A_), and which, like these, are formed shortly before the pollen sacs open The pollen spores (Fig 81, _I_) are large, oval cells, having a double wall, the outer one somewhat heavier than the inner one, but sufficiently transparent to allow a clear view of the interior, which is filled with very dense, granular protoplas that here also there is a division of the spore contents, although no wall is present The spores do not germinate very readily, and are less favorable for this purpose than those of so the best for this purpose are the spiderwort (_Tradescantia_) and _Scilla_

Owing to the large size and consequent opacity of the ovules, as well as to the difficulty of getting the early stages, the development and finer structure of the ovule will not be discussed here The full-grown ovule eneral idea of its structure obtained A little potashit ahen the section is sufficiently cleared We find now that the ovule is attached to a stalk (funiculus) (Fig 81, _G_, _f_), the body of the ovule being bent up so as to lie against the stalk Such an inverted ovule is called technically, ”anatropous” The ovule is ed where the stalk bends The upper part of the ovule is on the whole like that of the pine, but there are two integule one found in the pine

As the seed develops, the ees so as to occupy pretty much the whole space of the seed At first it is nearly filled with a fluid, but a layer of cells is for the walls, and this thickens until the whole space, except what is occupied by the small embryo, is filled with them These are called the ”endosperymnosperms, in the fact that they are not developed until after fertilization, and can hardly, therefore, be regarded as representing the prothalliuymnosperms and pteridophytes

These cells finally form a firm tissue, whose cells are filled with starch that forms a reserve supply of food for the e 81, _K_, _e 82, _J_), even when the seed is ripe, remains very small, and shows scarcely any differentiation It is a small, pear-shaped mass of cells, the smaller end directed toward the upper end of the eroith the e the shell of the seed The stalk of the ovule also enlarges, and finally fore of the seeds already noticed (Fig 81, _J_, _K_)

CHAPTER XVI

CLassIFICATION OF THE MONOCOTYLEDONS

In the following chapter no atteive an exhaustive account of the characteristics of each division of the monocotyledons, but only such of the most important ones as may serve to supplement our study of the special one already exahout the spermaphytes, is based mainly upon the characters of the flowers and fruits

The classification adopted here is that of the German botanist Eichler, and seee of the relationshi+ps of the groups than do the syste to Eichler's classification, the roups; viz, I _Liliiflorae_; II _Enantioblastae_; III _Spadiciflorae_; IV _Glumaceae_; V _Scitamineae_; VI _Gynandrae_; VII _Helobiae_