bc, etc., are called Phytons (from the Greek Pozót, plant), or plant elements. Observe that the leaf a emerges from the left hand of the stem, and the leaf b on its right hand, but above a; when leaves grow in this way, they are called alternate. If the leaf 6 had been brought downward, so as to be on the same horizontal plane with it, the leaves would have been said to be opposite. We have said that the horizontal section of the stem of a grass was a circle. Like all circles it contains 360 degrees. The leaf b is therefore inserted at a point one-half the circumference of the stem, or 180 degrees from a; but above it, in like manner, the leaf c is above b, and 180 degrees from it, and in the same way d is above c, and 180 degrees from it, and so on to g. The leaves, therefore, are arranged spirally on the stem, and are all separated 180 degrees from each other. It follows from this that the third leaf will always be vertically over the first leaf. Thus e is the third leaf from a, and is vertically over it; e is the third leaf from c, and is vertically over it. A plumb line let fall from e would exactly coincide with c and a. Plants that are arranged in this way are said to be two ranked. This arrangement should be carefully borne in mind, as the phrase will be used hereafter.

5th. The nerves of the leaf are parallel to each other, not branched. This mark is common to all monocotyledons. Any one who will look on the under side of the leaf of a corn stalk or any grass will see more or less protuberant ribs running the entire length of the leaf. These ribs are called nerves when speaking of the grasses.

6th. The dilated petiole, or sheath, surrounds the stem from the node to the blade, and is furnished with a more or less manifest scarious appendage called a ligule. The slit in the sheath is a very important mark of distinction between the grasses and the sedges. We believe there is not a single sedge where the sheath can be separated from the culm without tearing. Some of these terms may require some farther explanation to make them intelligible to begin ners. The petiole is the stalk upon which the leaf is supported, and which connects it with the branch. In most plants it is solid, but it is modified in the grasses, as may be seen in figure three. It is flattened, and surrounds the stem from the node to the ligule; but is slit down all the way, and cannot be opened without tearing it. When the petiole assumes this form it is called a sheath. Scarious means a thin, dry, membrane-like substance. The pith of a goose quill is

scarious.

The

They are outer pair

7th. The flowers are generally perfect or monorius. imbricated with two ranked glumes or bracts.

(glumes, see figure 6), subtending a spikelet (figure 4) of one or several flowers; the inner pair (paleæ figure 5), inclosing each particular flower which is destitute of a proper perianth. Stamens vary from one to six. There are usually three (figure 7). The anthers are versatile and variously colored. The ovary is one celled and one ovuled, usually having two to three scales at the base. The styles are mostly two or three parted. The stigmas are plumose. The spikelets are either paniculate or spiked. Several words in this seventh characteristic of a grass must be explained. A perfect flower is one that has both stamens and pistils. Monacious, when both the stamens and pistils are borne on the same plant. Imbricated is when one covering overlaps the other, as shingles on a roof, breaking joints. The perianth is the covering of the stamens and pistils. It sometimes consists of the calyx alone, and sometimes of the calyx and corolla. The anther is said to be versatile when it is attached to the filament at a point near its center, so that it can swing to and fro freely. Spikelets are said to be paniculate when they grow upon secondary branches. When the spikelets grow upon the main branches they are said to be racemed. Flowers are spiked when they grow directly from the rachis without branches. The other terms made use of will be readily understood by an examination of the figures referred to. These seven characteristics, taken together, constitute substantially the definition of the grass family, as given by Dr. Dar lington, and we have met with none which we think more clear and accurate. Whenever we see a plant which presents this assemblage of characters, we shall know that it is a true grass. Whenever we fail to find this assemblage of characters, we may be sure that it is not a true grass.

The only families of plants that the beginner will be likely to confound with the grasses are the sedges and rushes. We will, therefore, point out a clear mode of distinguishing them from each other. We have seen that the sheath of the grass is split through its whole length and can be removed from the stem without tearing it, while the sheath of a sedge is not split and connot be removed from the stem without tearing. This gives us a very clear and intelligible means of distinguishing between them. We have already stated that the leaves of all the grasses are distichous or two ranked. We have now to state that all sedges are tristichous or three ranked. What this means we will now explain. On examining figure two it will be seen that the first leaf emerges at 1, the second at 2, and the third at 3, and the fourth at 4. There are, therefore, three leaves

on the circle, each leaf being higher on the stem than its predecessor. There is, therefore, an interval of 120 degrees between the leaves, and the fourth leaf is vertically over the first. All the leaves of a sedge are spirally arranged around the stem with this constant interval between them. This is what is meant by a three ranked arrangement. Any one who will take the trouble to remember it can never mistake a sedge for a grass. Rushes, when their leaves resemble grass, as in the genus Luzula, have flowers composed of six parts or points, within which lie six stamens and a triangular ovary containing three seeds, while a grass has but one seed in the ovary. When, therefore, the plant has more than one seed in the ovary, you may be sure that it is not a grass.

We have said that the grasses form a very natural division of the vegetable kingdom; it is this fact which causes the difficulty of discriminating between the individual species. When we say that the grasses form a very natural division, it is equivalent to saying that they all have a great deal in common; it is therefore evident that those things which they do not have in common must be sought for with great care in order to identify the species.

Since one species of grass is distinguished from every other species, by certain peculiar properties, such as the number, situation, proportion, and color of the different parts of the structure, we must be well acquainted with these properties, and with the precise names of the several parts.

STRUCTURE OF THE GRASSES.

In the grasses, we meet with the following parts. Although they are tolerably constant in form in individual grasses of the same species, yet they vary so much in different genera, as to afford characters sufficiently distinctive for their separation. They are:

1. THE ROOT, or descending axis. This organ is modified, and named as follows:

(a). Fibrous, when the root is composed of a number of threads or fibres, as in Poa annua, or Poa trivialis. We give, in Fig. 8, the fibrous root of Rottbolia filiformis as an example of this form, but the student should not depend upon figures, but examine the roots themselves.

(b). Creeping, when the root runs horizontally in the earth and pushes up stems from the joints with which it is furnished, as in quack grass (Triticum repens), and in wire grass (Poa compressa), a very good illustration of this form is given in Fig. 9, which represents the root of the small water hair grass (Catabrosa aquatica).

(c). Bulbous, when the root consists of a solid substance in a spherical form, as in Hordeum pratense, when it grows in barren grounds that are occasionally overflowed, and in Phleum alpinum. This form is illustrated in Fig. 10, which represents the root of Phleum pratense (variety longiaristatum), and Fig. 11, which is the root of P. pratense (var. longiciliatum), which shows a succession of bulbs. The roots of grasses are mostly of the kind known as "fibrous," indeed these are the only true roots, as these are the only organs that extract nourishment for the plant. The creeping part of the root, or rhizome, as it is called, is simply an underground branch, and not a proper root. All plants receive their food from fibrous roots alone, the rhizome and the bulb are organs added to the true root, and are not really essential parts of it. Bear it in mind that true roots never have any buds upon them; if, therefore, we meet with any underground growth that has buds on it, we may be sure that it is not a

true root.

The root extends by successive elongations, being continued by protrusion outward, like the inner joint of a telescope from the outer. This form of development, which is called by botanists Endorhizal, (from two Greek words signifying "from within a sheath") may be well observed in the germination of the larger cereal grasses, such as wheat, barley, &c. Some of these extend to very great lengths in search of food and moisture, branching off into innumerable fibrils or rootlets, the ends of which, consisting of the newest cells or growths, form the spongioles or suckers, by which the nutriment is conveyed from the soil into the plant system. The fibrous roots of the grasses vary very much in their appearance; some are hairy, some are very much branched, some are very little branched, some are straight, and some are sinuous. The attentive observer will soon learn to recognize a species of grass from seeing the root nearly as well as he can from seeing the plant. Rhizomes will sometimes creep along under the ground for a very considerable distance. We have seen one of these from a stem of quack grass (T. repens), six feet in length. The function of the bulb in bulbous grasses seems to be to store up materials for the future growth of the plant. The differences among the roots of the different species frequently afford us distinctive characters when all other means fail. Thus the external appearance of the flower in Poa pratensis and in P. annua is exactly the same. We usually recognize the difference between them at a glance, because the latter is much shorter and yellower in color than the former; but in some situations P. annua grows much taller, and is of a darker green, so [AG.]

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that we are in doubt as to whether we have a short P. pratensis or a tall P. annua. In this case the usual way is to pull one of the flowers carefully from the spikelet; if there is found something hanging from the base like a cobweb, we say that it is a P. pratensis, if there is no web at the base, we say that it is a P. annua., But in some rare instances we have seen a little web on the base of P. annua, and sometimes it is very difficult to find the web of P. pratensis. In order, now, to determine the matter we resort to the root; if it has a rhizome it is certainly P. pratensis; if it has a fibrous root it is surely P. annua.

2. THE CULM, STRAW OR STEM.-The ascending axis of a grass is called by these names indiscriminately. It will be remembered that this part is hollow, cylindrical, separated into long or short lengths by the intervention of nodes which are solid, and which tend much to strengthen its structure. It is evidently to accomplish this object that the nodes are placed near to each other at the lower part of the stems, where the strain is greatest in consequence of their swaying backward and forward in the wind, and more remote upward from which the newer and more delicate leaves are supsended. Culms afford several points of comparison and distinction between different species of grass. Some are quite smooth and glossy, others are deeply ribbed, others are armed through their entire length with hairs, or they may only be found on parts; which hairs may be long or short, bristly or downy, according as this kind of armature is coarse or harsh, or fine or soft. The nodes may be of a different color from the culm, or like it; may be armed with a similar variety of hairs, or may be perfectly smooth. The nodes in some species swell out beyond the circumference of the culm, or may be of less diameter than it, or just equal to it; in either of these cases they afford good grounds of comparison.

3. THE LEAVES consist of the following parts:

(a) The sheath, or modified petiole.

(b) The Ligule or tongue.

(c) The Lamina. The blade or flat part of the leaf; that which, in common speech, is called the leaf,

The sheath is not only the foot stalk of the leaf, but also performs the functions of the leaf itself. Like it, it is provided with a perspiratory apparatus, and like it, it stores up chlorophyl, starch and sugar; throughout its whole length it enwraps the culm, and may be easily disengaged from it without tearing; a circumstance which, as we have already said, serves to distinguish the grasses from the sedges,