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OF THE STEMS AND STALKS OF PLANTS.
ed by buds as commodiouşly as by roots. ing, or zigzag; either alternately branched Those of one tree may be engrafted on the, or oppositely; two-ranked, when the branches bark of another of the same species, or one spread in two horizontal directions, or branearly akin, by which, as is well known, chiate, four-ranked, when they 'spread in valuable varieties are multiplied. Fig. 8. fonr directions, crossing each other alter
It is remarkable that nature should per- nately in pairs. Caulis determinate ramosus, mit such devastation and waste as is made an abruptly branched stem, belongs partihy many insects, whose caterpillars or grubs cularly to the heaths, the rhododendron, &c. feed on the buds of trees. Several species and is a term invented by Linnæus to exof fir are infested with their appropriate in- press their peculiar mode of growth; each sects, which, literally speaking, devour their of their branches, after terminating in vitals, and should seem to be capable in one fowers, throws out a number of fresh as. season of destroying a whole forest. Yet ceniling shoots from just below the flower. these are only instruments in the hand of ing part. The Indian fig has a remarkable Providence, which, like many others, though jointed stem, whose ovate portions look like formidable in appearance, are never allowed leaves; possibly the scales with which they to transgress their due bounds.
are covered may be equivalent to leaves.
The shape of a stem is either round or
two-edged, as in the everlasting pea, or Botanists reckon seven kinds of stems or
with three, four, or more angle Square stalks of plants.
stems are extremely common, and such ge1. Caulis, a stem, fig. 9, properly so nerally bear opposite leaves. Several stems called, bears both leaves and flowers, are winged, the angles being extended into as the trunks and branches of all trees and leafy borders, as in thistles. shrubs, as well as of many herbaceons plants The stuface of the stem is either smooth, besides. By its means the organs of plants rough, warty, viscid, bristly, hairy, downy, are raised to a commodious height above woolly, hoary, or glaucotis. It is either strithe ground, and presented in various direc- ated with fine parallel lines or more deeply tions to the atmosphere and light. In ger- furrowed; sometimes it is spotted with a mination, it always takes a contrary direc- purplish hue. tion to the root. As it advances in growth, The inner part of the stem is either solid, it is either able to support itself, or twines in which case its centre is occnpied with round, or adheres to other bodies. Some pith; or hollow, and lined with a white stems creep on the ground, and take root shining membrane, of which the hemlock is here and there, by which the plant is in- an example. When the stem is wanting, a ereased. The stem is either simple, as in plant is called acaulis, as is the case with the lily, or branched as in the generality of the daisy and primrose. The vature of the plants. When regularly and repeatedly stem agrees in many respects with the caudivided, with a flower springing from cach dex, or body of the root, at least in trees division, it is called caulis dichotomus, a and shrubs ; for such are capable of being forked stem. Though generally leafy or propagated by cuttings of their stem or scaly, a ştem may be naked in plants desti- branches, which, when planted, throw out tute of leaves altogether, as the creeping roots. This is not the case, however, with cereus, and the genus Staphelia, Climbing annual stems. Linnæns calls the stems of stems are of several kinds; as radicans, trees roots above-ground. It is frequently clinging to any other body for support by indifferent which end of a cutting is plauted means of fibres which do not imbibe nourish. in the earth; and the extremity of a branch ment; scandens, climbing by means of spiral bent down to the ground in most cases reatendrils like the vine and passion-flower; vo- dily takes root, wliich circumstances conlubilis, twining round any thing that comes firm his idea. in its way by its own spiral form, either The stem of several plants is subject to from left to right, according to the appa a disease, whence it becomes as it were rent motion of the sun, like the boneysuckle, compound or elustered, forming a broad or from right to left, like the convolvolus and Aat figure, crowded with leaves or flowers French bean; nor can any art or force at the extremity, and sometimes besprinkled make a twining stem turn contrary to its with them at the sides. We have seen it in natural direction. In the manner of their the ashi, holly, broom, nasturtiuis, wallgrowth and branching stems are very vari- flower, toad-fax, &c. A kind of pea is fre. ops, being cither straight, irregularly spread- quently cultivated in Norfolk with red and
I Fibrous Root Cran. 2 treeping Root Mind, 2 Spindleshapid Root Radish. 4 Abrupt Root, Scabiosa, Succisa. 5 Tuberous Rootlbtake. 6 Bulbous Roete OnionW Litty. 7 Granulested Root Sarithaga Granulakl. 8 Bud Ilerve Chemut - Stem. Bowing haver Flower Carolul 10 Sinww Gra Il Siatki Passion Flower.. 12 flower suik. 13 Foot Stalk. 18 Stipula, 19 Practia. 22 Tendril. 23 Gland.
Cooper feelp. Lenden Published Feb 1808 by Loaşman llurst Rev & Orme Paternoster Row.
OF THE LEAVES.
white Aowers, and a tender eatable pod, The sap-vessels are for the most part very called the top-knot pea, in which this va conspicuous in foot stalks, and their spiral riety of stem is regularly propagated by coats are easily observed. seed.
6. Frons, a frond. This term, which 2. Culmus, a straw, or cnlm, fig. 10, is properly means a bough, is technically apthe peculiar stem of grasses, rushes, and plied by Linnæus to express the stem, leaf, such like plants. It bears both leaves and and fructification being united, that is, the flowers, and in that respect comes under leat bears the flowers and fruit. The term the denomination of a caulis; but is readily is only used in the class Cryptogamia. known by its babit, though difficulties at Ferns which bear seeds on the back of their tend its definition. In most grasses, corn, leaf are genuine instances of this, and it is &c. it is jointed in a manner peculiar to it- applied to lichens, &c. Plate II. fig. 14. self, and then cannot be mistaken; but in 7. Stipes, stipe, is the stem of a trond, tig, common rushes, and some few grasses, it is 15, or the stalk of a fungus, as in the comdestitute of joints. When these parts are mon eatable mushroom. In the former inbent, it is called geniculate, and such joints stance it is very generally clothed with readily take root.
scales of a peculiar chaffy texture; in the 3. Scupus, a stalk, fig. 11, springs imme latter it is very often invested by a ring diately from the root, bearing flowers and formed of the membrane which had previfruit, but not leaves, as in the primrose and onsly covered their fructification. cowslip. It is either simple or branched, naked or scaly. In the cyclamen it becomes spiral after flowering, and buries the The leaf, folium, fig. 16 and 17, is a very seeds in the ground. Dr. Smith has found, general organ of vegetables, yet not absocontrary to the opinion of Linnæus, that a lutely necessary to all plants, for the stems plant may sometimes be increased by its and stalks occasionally perform its functions. scapus, as in lachenalia tricolor, which oc What those functions are we shall in a comcasionally bears bulbs on its stalk.
pendions manner explain. Leaves are gene4. Pedunculus, the flower-stalk, fig. 12, rally so formed as to present a large surface springs from the stem or branches, bearing to the atmosphere; when they are of any flowers and fruit, but not leaves. Pedicellus other hue than green, they are said in botaniis a partial Power-stalk, or, in other words, cal language to be coloured. Their duration the ultimate subdivision of a general one. is for the most part annual, but in some trees The most common situation of a flower and shrubs they survive two or more seastalk is axillary, originating from between a sons, and such plants being always in leaf leaf and the stem, or between a branch are denominated evergreens. The internal and the latter. It is rarely opposite to a surface of a leaf is highly vascular and pulpy, leaf, as in some species of geranium, and and is clothed with a cuticle very various in still more rarely intermediate between two different plants, but its pores are always 30 leaves, as in some kinds of solanum. It is constructed as to admit of the requisite either terminal or latera!: solitary, cluster- evaporation or absorption of moisture, as ed, or scattered; simple or branched. Ac well as to admit and give out air. Light cording to the various modes in which it is also acts through this cuticle in a definite subdivided several kinds of inflorescence
That air and moisiure and light are distinguished, to be mentioned hereafter. have considerable, and even the most imSessile tlowers are such as have no stalk. portant effects, npon the leaves of plants, The flower-stalk is occasionally nakeil, or has long been known to those who have stufurnished with bracteas. Very rarely it died the subject; that heat and cold affect bears tendrils.
them is familiar to every one. 5. Petiolus, the foot-stalk, fig. 13, is ap- riments of Hales, Bonnet, and others, have plied exclusively to the stalk of a leaf, and thrown much light upon the absorption and is either simple, as in all simple leaves, or perspiration of leaves, wiile those of Priestcompound, as in the greater part of com ley and Ingenhouz have explained their ef: pound ones. Sometimes it bears tendrils. It fects upon the atmosphere, and the manner is generally channelled on the upper side, in wbich air and light particularly act upon and more or less dilated at the base; in one them. Leaves have a natural tendency to or two instances the flower-stalk grows present their upper surface to the light, and out of it, as in turnera. Leaves that have turn that surface towards it in whatever di. no foot-stalk whatever are called sessile, rection it is presented to them. When
trees in leaf are nailed to a wall, and the po- leaf itself, for the common sap of plants, sition of their leaves is consequently dis- from which all their secretions are made, turbed, they soon recover their natural di differs very little in plants whose qualities rection. Light evidently acts as a whole are very unlike to each other ; those qualisome stimulus to their upper surfaces, and ties depending upon the secreted fluids elaas a hurtful one to the under. When the borated principally by the leaves. latter is forcibly presented for a long period The green colour of the organs in question to its rays, destruction is the consequence. is easily proved to be almost entirely owing Leaves seem to require occasional repose to the action of light. Plants which grow in from the action of light on their upper sur the dark are of a sickly white, which is the face; for, when it is withdrawn from them,
case with any parts artificially or accidenmany leaves close or fold themselves toge- tally covered with earth, as in cultivated ther, as if in a state of relaxation, and spread cellery or asparagus, whose stems and leafthemselves forth again at the returning stalks are purposely managed in this way to beams of the morning. This is more espe- render their flavour and appearance more cially the case with winged leaves, as those delicate. Such blanched parts soon beof the pea kind. Those of the white aca
come green on exposure to light. Leaves cia, robinia pseudo-acacia, have been re are subject to a sort of disease by which marked by Bonnet to be over-excited by they become partially spotted or streaked the sun of a very hot day, and to fold their with white or yellow. In this state they upper sides together, in a manner directly are termed variegated, and occasionally contrary to their nocturnal posture. The contribute to the ornament of our gardens. effect of moisture upon leaves every one The wliiteness frequently extends to the must have observed. By absorption from leaf-stalk, and sometimes to the branch, as the atmosphere, they are refreshed, and by may be seen in the variegated elder. Such evaporation, especially when separated varieties are propagated by cuttings, layers, from their stalks, they soon fade and wi or roots, but not by seed. They appear to ther. Aquatic vegetables, whose leaves are be somewhat more tender than the plant in immersed in the water, both absorb and its natural state. One variety of the bolly perspire with peculiar facility. Anatomical has, in addition to a yellow variegation, a investigations have shewn that the nutri beautiful tinge of purple, but this is a rare tious juices, imbibed from the earth, and instance. In the amaranthus tricolor the become sap, are carried by appropriate leaves are naturally adorned with most beauvessels into the substance of the leaves. Mr. tiful and splendid colours, and in some Knight, in his papers in the Philosophical other species of the same genus, with inore Transactions, has demonstrated that these uniform and less vivid tints. juices are returned from each leaf, not into The irritable nature of some leaves is rethe wood again, but into the bark. Hence markable, not but that all leaves may truly a new and curious theory of vegetation bas be said to possess irritability with respect to been established. It appears that the sap light. The phenomena however to which is carried into the leaves for the purpose of we now allude are of the most striking kind. being acted upon by air and light, with the The sensitive plant, mimosa pudica, common assistance of heat and moisture. By all in hot-houses, when touched by any extrathese agents a most material change is neous body, folds up its leaves one after wrought in its component parts and quali- another, while their foot-stalks droop as if ties, differing widely according to the di- dying. After a while they recover them. versity of the species. Thus the resinons, selves again. Each leaf of the dionæa muoily, mucilaginous, saccharine, bitter, acid, scipula, or Venus's fly-trap, is furuished or alkaline secretions are elaborated. The with a pair of toothed lobes, which, when heedless observer of a leaf is little aware of touched near the base, fold themselves toge the wonderful operations constantly going ther and imprison any insect that may be on in its delicate substance, nor can the in their way. It is presumed that the air most enlightened philosopher explain more evolved by the body of the dead insect may than a very small part of the chemical pro- be wholesome to the plant, for leaves are cesses of which it is the immediate agent. It known to purify air impregnated with car. is scarcely necessary to observe how mate bonic acid gas, produced from the breathing rially plants differ in the flavour and quali- of animals or the burning of a candle. The ties of their leaves, all which must depend in sarracenia, of which several species from a great measure on the operation of the America are now cultivated in our more