Part IV

to atropine. The tomato and tobacco plants also belong to this Order, CHAPTER XXXIII. OOMPOSITiE. I. The Coinpositse is the most extensive Order, and comprises from 10,000 to 12,000 species, or roughly about one-tenth of all known seed-bearing plants. A number of species, such as Arnica montana L., chamomile and wormwood, are of medicinal value ; others, of which the artichoke and lettuce may be taken as examples, are useful food plants of the garden. Plants belonging to the genera Zinnia, Chrysanthemum, Dahlia, Aster, Gaillardia, Helianthus, and others are largely grown as ornamental plants. Not a single species, however, is grown as an ordinary farm crop in this country, though not a few, such as dandelion, thistle, groundsel, coltsfoot, mayweed, and ox-eye daisy are objectionable weeds (see pp. 592, 605^. -- 2. General characters of the Order. The most characteristic feature of the Order is the structure of the inflorescence : the latter is a capitulum, and consists of a number of small flowers collected into a compact head resembling a single large flower. A common form of capitulum is seen in the ox-eye daisy (Fig. 147), the parts of which, with the dandelion described below, may be taken as typical of the commonest forms in the Compositae. On its underside is a series of narrow scaly bracts termed phyllaries, arranged in whorls; the whole series of phyllaries is spoken of as the involucre of the capitulum. In the centre of the capitulum are a number of small yellow -- -- flowers the so-called disk florets each of which has the ; GENERAL CHARACTERS OF THE ORDER 471 form shown at 2, Fig. 147. Each floret or small flower is regular and epigynous ; the corolla gamopetalous and five-lobed no calyx exists, or is only present in the form of a minute ring round the upper part of the ovary. The androecium consists of five stamens with filaments attached to the inside of the corolla (epipetalous) ; the anthers of the stamens are united together, and form a tube through which the style passes. (Stamens with united anthers and free filaments are described as syngenesious.) The ovary is inferior and syncarpous, consisting of two united carpels ; within it is a single erect anatropous ovule. The straight style has a divided tip. -- Fig. 147 I, Capitulum of Ox-eye Daisy CCA?:J'ja�^>5ff- inujn Leucanthemutn\j.'). r The 'ray'; rf the 'disk.' 2. ' Disk ' floret (magnified), o The ovary ; c tubular corolla ; a anthers ; s stigma. 3. ' Ray ' floret (magni- fied), o Ovary ; s stigma ; c ligulate corolla /"fruit. , The fruit (/, Fig. 147) is one-seeded and indehiscent with a series of longitudinal ribs on its outer surface r it is a kind of nut or achene to which the special name cypsela is given. The seed is without endosperm. Besides the disk florets and surrounding them, there is a single ring of white flowers (f) resembling narrow strap-like petals. They form the ' ray ' of the capitulum, and are termed ray florets. Each of the latter is a small unisexual (female) flower, and possesses a white corolla, the lower part of which is tubular, while the upper part is drawn out into a long narrow 472 COMPOSITE A structure, the tip of which is notched (3, Fig. 147)- corolla of this form is described as ligulate. The rest of the parts are similar to those of the disk florets. Both the ray florets and the disk florets are sessile upon a short, thick button-shaped axis which is designated the receptacle of the capitulum, an unfortunate term likely to be confused with the receptacle of a flower, with which however it has nothing to do. A large number of genera, the species of which have capitula composed of tubular florets only, or of tubular florets and an outer whorl of ligulate florets, are united to form a division of the Compositse known as the TubulifloR-�. Plants belonging to this series have watery juice in their stems and leaves. Another group of genera, termed the Liguliflor^, is formed of those species whose capitula bear only ligulate flowers. Plants belonging to the Liguliflorae, of which the dandelion and sow-thistle are examples, have milky juice (latex) in their stem and leaves. A single flower from the capitulum of the dandelion is seen in Fig. 148. It is bisexual with a ligulate corolla formed of five petals shown by the five notches Fig. 148.--I. Single Floret of Dandelion {Tar- axacum officinale Web ). o Inferior ovary ; fi pappus (calyx) ; a anthers of stamens ytheir ; Ataments ; � style and divided stigma ; c ligu- late corolla. 2. Fruit (cypsela) developed from i. s Stalk of the pappus j^. 3. Fruit (cypsela) of Groundsel (Seiucio vulgaris L.) with sessile pappus. flowers when the fruit is ripening: at its tip. The calyx is composed of silky hairs which encircle the upper part of the ovary. This ring of hairs grows most rapidly after fertilisation of the it is termed tht pappus, and acts as a parachute for the distribution of the fruit by the wind. YARROW : MILLEFOIL OR THOUSAND-LEAF 473 In the dandelion the pappus is stalked, that is, situated at the end of the prolonged upper part or beak of the fruit (2, Fig. 148). In groundsel (3, Fig. 148) the pappus is sessile. -- Ex. 245. (l) Examine the inflorescences of ox-eye daisy, common daisy, sow-thistle, dandelion, groundsel, and any other common Composite. Note the form and extent of the involucre, the presence or absence of disk and ray florets. (2) Cut vertical sections of the capitula and observe the form of the receptacles, whether flat, convex, concave, or conical. Note the presence or absence of small bristly or chaffy scales (bracteoles) on the receptacles near each flower. {3) Examine the fruits of the above-mentioned plants. Note (he presence or absence of a pappus ; also the smoothness or roughness of the pericarp. Are the hairs of the pappus simple or branched ? 3. Yarrow : Millefoil or Thousand-leaf {Achillea Millefolium L.) is a perennial plant belonging to the Compositse, common in poor dry pastures, and possessing an extensive creeping rootstock. The stems are from 6 to 18 inches high, and furrowe-d. The leaves are 2 or 3 inches long, narrow, oblong, and much divided, the segments being very fine. The capitula, which are crowded together in a corymbose manner, are small, usually not more than or ^ inch in diameter, with white or pinkish -J- ray florets. The fruits, commercially known as ' seeds',' are compressed, and have no pappus. Yarrow grows very early in spring, and possesses a strong aromatic odour when bruised. Sheep are fond of the young leaves, and generally keep the plants eaten down in pastures. But when it has developed its strong woody stem stock refuse it. Yarrow is sometimes recommended for mixture with grass seeds when sowing down land for sheep pasture, but its use must be restricted to the narrowest limits, or it will soon disfigure and usurp the ground which should be allotted to better 474 COMPOSITyE plants. It should be left out of all grass mixtures where the produce is to be mown. -- Ex. 246. Dig up and examine a complete plant of yarrow in flower. Note the character of the rootstock, its tough stem and much divided leaves, and its corymbose collection of small capitula. Carefully examine a single capitulura, noting the number and form of the ray and disk florets respectively. Examine the fruits of yarrow. CHAPTER XXXIY. GRAMINE^. TRUE GRASSES. -- I. General characters of the Order. Herbs. Roots fibrous, chiefly adventitious. Stems cylindrical, hollow, with solid nodes. Leaves alternate with split leaf-sheath and ligule. Inflorescence a spikelet, bearing chaffy bracts or glumes, which hide the flowers. Flower small, bisexual, hypogynous. Perianth missing, or consisting of two scales (lodicules). Androecium of three stamens with versatile anthers. Gynsecium a single carpel, with two feathery or brush-like stigmas ; ovary with one seed. Fruit a caryopsis. 2. This is one of the most valuable and extensive Orders- of plants, and comprises between 3000 and 4000 species. To it belong the cereals which supply the chief part of the food of the human race, and also the meadow and pasture grasses so important as food for the stock of the farm. The general character of the roots, stems, leaves, and flowers of grasses are here dealt with, while in the subsequent chapters the cereals and those grasses of which it is essential that the agriculturist should possess a good knowledge are treated in greater detail. -- Root. The roots which emerge from the seeds of grasses on germination are few in number and short-lived, but an extensive system of adventitious, thin, fibrous roots develops later from all the underground nodes of the stems. -- Stem. The stems, which are termed culms, are cylindrical and usually hollow when full-grown, except at the nodes, where 476 GRAMINE^. TRUE GRASSES they are solid : maize is exceptional in having stems solid throughout. Branches arise only in the axils of the lowermost leaves. ' Tillering ' is the term employed to designate this form of branching in grasses, and its nature is discussed on pages 482-485. Generally the buds break through the base of the enclosing leaf-sheaths ; the branches produced are designated extravaginal branches and grow more or less horizontally for a time, often underground, forming longer or shorter rhizomes, from which leaves and flowering stems are sent up. Grasses behaving in this manner soon cover considerable areas of the ground with a close turf Couch-grass, smoothed-stalked meadow-grass, and florin are good examples. Less frequently the branches are intravaginal, that is, they grow up between the leaf-sheath and the stem, emerging near the ligule, but ultimately, tearing the subtending leaf, as in i, Fig. 153. Branching of this character leads to the formation of compact tufts, and grasses exhibiting this manner of growth are unable to cover the ground except in isolated patches. The cereals (see pp. 482 to 485), annual brome-grasses, meadow and sheep fescues, rye-grasses, and cocksfoot are examples. The perennial rhizomes of grasses are usually sympodia (2, Fig. 22). -- Leaf. The leaf of a grass consists of two parts, the blade and the sheath. The leaf-sheath surrounds the stem like a tube split down one side, its free edges overlapping in some instances (^,Fig. 149). In cocksfoot, dodder-grass, and some of the meadow- grasses it is not split but forms a completely closed tube. It acts as a support for the stems while they are young and soft, and protects the tender growing points within from the injurious effects of frost and heat. Most grasses appear swollen at the nodes {d. Fig. 149); this is not usually due to thickening of the stem, but to the presence of a mass of soft tissue at the base of the leaf-sheath. a. :� , . ,,.,,,, J TVTodes leaf-sheath sh^^?-/tlTMfnX\nTn'?;SSe^�ce^;n �%�5-V/^). of ; /j leaf-blade; which a U the /"ligule; rachis;. branches of rachis ; c spikelels. ; 478 GRAMINE^. TRUE GRASSES The leaf-Made is generally long, narrow, and flat, but in grasses growing in dry places it is often folded and appears almost cylindrical (Fig. 183). The first leaf of the embryo and those upon the underground rhizomes are almost always modified structures representing leaf- sheaths the blades of which remain undeveloped or rudimentary. It is important to notice the arrangement of the leaves in the bud as it often affords a ready means of distinguishing nearly - allied species of grasses. Most frequently the leaves are rolled up from one side in a spiral form, and the young shoot appears round (Fig. 191), but in several grasses they are simply folded down the middle, the shoot then appearing flattened (Fig. 188). At the point where the blade joins the sheath the inside of the latter often protrudes as a tongue-like membranous structure (/ -- 3 4 . Fig. 150. I. Spikelet from grass of Fig. 149. 2. The same slightly opened to show separate glumes and florets, a Empty glume ;yfiowering glumeof second floret; rrachilla or axis of spikelet. y 3. Single floret of 2. Flowering glume \p palea o ovary of gynaecium ; r piece of rachilla. 4. The flower. I Lodicules ; o ovary ; j stigma ; a stamen. Fig. 149), termed the ligule. The latter varies much in length in different species. Near the ligule the sides of the leaf sometimes terminate in claw-like projections which partially or entirely encircle the stem as in Figs. 154 and 189. -- Inflorescence. In the figure of annual meadow-grass (Fig. 149), the branched upper part popularly termed the 'flower' is a complex inflorescence bearing flowers which are very small and completely hidden from view. The parts c are termed spikelets, and it is within these that the flowers are enclosed. A On single spikelet is illustrated in Fig. 150. examination it is seen to consist of an axis r, the rachilla, upon which is GENERAL CHARACTERS OF THE ORDER 479 arranged a series of sessile bracts in two alternate rows. These bracts are termed glumes, and in the axils of all except the two lowermost ones (a a) flowers are produced which on account of their small size are not seen. The glumes a a are termed the / empty glumes of the spikelet, the others similar to are the flowering glumes. Attached to the very minute stalk which each flower possesses is another bract, named the/a/i? or palea seen at /. It lies opposite to the flowering glume, and between it and the latter the flower is enclosed more or less completely. The empty glumes are usually two in number, but there is only one in rye-grass, and the spikelet of sweet vernal-grass possesses four. Sometimes they are small and narrow as in rye, or they may be large and completely enfold the rest of the spikelet as in oats. The flowering glumes often differ from the empty ones in having ' beards ' or bristle-shaped structures termed aivns. In barley and ' bearded ' wheats the awns are of great length, while in some instances they are merely short points at the tip of the glume. Awns are said to be terminal, dorsal, or basal according to whether they arise from the tip, middle of the back, or the base of the glume. The number of flowers in each spikelet varies considerably : in some species, as timothy grass and florin, only one is present, in Yorkshire fog two, while in meadow-grasses, fescues, and rye- grasses there are several. All our grasses resemble each other in having their flowers in spikelets, the latter, however, do not constitute the whole inflorescence but are only parts of it. In wheat, rye-grass, and barley the spikelets are sessile upon opposite sides of a straight unbranched main axis, the rachis, the total inflorescence being termed a spike ; in reality it is a spike of spikelets. In the majority of grasses the rachis is much-branched and' 48o GRAMINE^. TRUE GRASSES the spikelets are borne at the ends of the branches as in Fig. 149. Such an inflorescence is termed z, panicle. When the branches of the panicle are long and the spikelets consequently separated from each other, the panicle is described as spreading, open, or diffuse (Figs. 174, 181, &c.). When the branches of the panicle are very short, so that the spikelets lie close to the main axis as in foxtail and timothy grass (Figs. 172 and r73), & false spike or spike-like panicle is formed. -- The Flower. As pointed out previously the glumes are bracts of the inflorescence and do not, of course, constitute a part of the flower. The latter (4, Fig. 1 50) consists of an androeciura of three hypogynous stamens and a gynaecium of one carpel. At the base of the ovary on the side opposite to the pale, that is, on the side next to the flowering glume, there are two small transparent scales, the lodicules, I; they are usually considered rudiments of the perianth, but may possibly represent a second palea. The filaments of the stamens are long and slender and attached to near the middle of the anthers ; the latter are readily moved by the slightest breeze. In sweet vernal-grass two stamens only are present. The gynsecium consists of a single carpel with an ovary most frequently surmounted by two brush-like styles (s). The grasses are cross-fertilised, though self-fertilisation is also frequent. At the time of flowering the base of the lodicules generally swell up and force the pale and flowering glume apart; the filaments of the stamens grow rapidly about the same time and push the anther out at the sides of the glumes ; the pollen is then distributed by the wind and caught by the feathery stigmas. In a short time (often not more than an hour or two) the lodicules lose their turgidity and shrivel, and the pale and flowering glume close up again shutting the ovary and stigmas from view. GENERAL CHARACTERS OF THE ORDER 481 -- The Fruit and Seed. The fruit of grasses is in most cases a caryopsis or a one-seeded form of nut, the seed of which has grown completely into union with its surrounding thin pericarp. The wheat grain discussed on p. 22 may be taken as typical of a caryopsis and its enclosed seed. In young flowers the ovaries of the grasses are quite free from the glumes and may remain so even when the fruit is ripe as in the case of wheat, rye and oats; sometimes, however, during growth after fertilisation the caryopsis grows up to between the glumes and becomes united with the latter as in the case of ordinary barley. In oats and many grasses the glumes so closely invest the caryopsis that the latter does not fall out from the glumes when the ripe panicles are shaken or thrashed ; nevertheless, in these cases the caryopsis is free and easily separable from the glumes, which is not the case in barley and many other grasses. The seed contains a large proportion of starchy endosperm, at the side of which the embryo is placed. In some grass seeds, and particularly those of certain varieties of cereal grains, such as Hard wheats, the endosperm is flinty, or hard and semi-transparent, while in others the endosperm, which is described as mealy, is opaque and chalky when cut across. The different appearance of flinty and mealy endosperm is due to the fact that in the first the starch grains within the" cells are embedded in a dense matrix of proteid material, while in the mealy endosperm the cells are not completely filled with reserve materials, but very minute air spaces exist between the starch-grains within the cells. The embryo (Figs. 7 and 151) possesses one cotyledon (the scutellum), a short plumule, and in most cases a single primary root covered by the coleorhiza. In the cereals and some other grasses secondary roots appear upon the very short hypocotyl of the embryo while the latter is still within the caryopsis and they make their exit at the same time as the primary root, when 2H 482 GRAMINE^. TRUE GRASSES germination commences; in most grasses, however, secondary roots first appear some time after the single primary root has grown out from the caryopsis. -- Ex. 247. Examine the roots of any grass. Observe as far as possible their origin, and note if they branch extensively. -- Ex. 248. Cut transverse and longitudinal sections of any well-developed grass stem at and between the nodes. Note if hollow or solid all through. Examine the leaves of barley and oats and many common grasses. Note the split leaf-sheath, the flat or rolled blade, and the character of the ligule if present. -- Ex. 249. Make an examination of the inflorescences of a number of common grasses in order to understand the various parts, viz., the lachis, and the spikelet with its rachilla and bracts. Which are the empty glumes, flowering glumes, and palea in each spikelet ? -- Ex. 250. Dissect out the flowers from any common grasses, noting the form and position of the stigma, the number of stamens, and the position, number and form of the lodicules in each. -- Ex. 251. Watch the unfolding of the total inflorescences of Yorkshire Fog, Tall Oat-Grass, and other grasses with panicles. What positions do the branches take before and after flowering ? -- Ex. 252. Cut transverse sections of several grains of barley, oats, wheat, rye and maize. Note the ' mealiness ' or ' flintiness ' of the endosperm in each. CHAPTER XXXV. GRAMINEiE [continued). CEREALS. In Europe perhaps the most familiar crops of the farm are wheat, harley, rye, and oats. These crops, designated Cereals, are grown mainly for their fruits or grains which form the most important food of mankind and are also of great value as food for the stock of the farm. Besides being utilised as bread-corn large quantities of the cereal grains are employed in the manufacture of starch, beer, whisky, gin, and other spirits. Moreover, the cereals are frequently grown for green fodder and the straw in a ripe state is fed to stock, made use of as litter, or employed for thatching, and many similarly useful purposes. The common cereals of the tropics are rice, maize, millet, and sorghum or dourra, but these, with the exception of maize, which is occasionally eqiployed in a green state as horse and cattle fodder or made into silage, have no practical interest for the farmer of this country. The cereals are grasses and therefore possess general char- acters described in the last chapter ; they are, however, of such importance that further treatment of their peculiarities is needed. -- Fruit and Germination of Seed. (a) An account of the fruit and the germination of the embryo of wheat has previously been given (chap, ii.) ; the grain of rye is similar to this in almost all respects, but the roots of its embryo are generally four in number instead of three as in wheat. (p) In barley the caryopsis or fruit is firmly united with the enclosing flowering glume and pale, and the plumule of the 483 484 GRAMINE^. CEREALS embryo does not make its exit where the coleorhiza and roots emerge but grows on beneath the glume, and ultimately appears at the opposite end of the grain sometime after the roots have come forth (Fig. 151). The number of roots vis- ible on the embryo within the barley grain is generally five or six. (c) In the oat the caryopsis is free from the glumes, but the latter more or less tightly surround it and on germination the plumule of the embryo behaves as in barley, and emerges from the grain at the end opposite to that at which the roots appear ; the number of roots of the embryo is three. -- Roots.- In the cereals, as in all grasses, the roots of the embryo within the seed ,,,'.,''. , ,. -- Fig. 151. Barley gram showing embryo and Its development during germination. 1. Longitudinal section of grain showing embryo at rest. 2. The same alter . . germination , has b, egun ; , the roots have made tlieir exit from the grain, but the plumule c is still within it enclosed by the flowering glume. 3. Later stage of the germinated gram showing the plumule c outside the grain. e Endosperm; a coleorhiza; i root; c plumule; (^scuteiium. g" row out when ogermination commcnces : these may ' be iexmed 'semifta/' roofs. They m are of imp^ortance the early life of the young plant, but , Subsequently ,. die -- off andn 1 their . work IS Undertaken by the so-called 'coronal' roots which arise