CHAMBERS'S INFORMATION FOR THE PEOPLE. 



descending axis, while the stem is the ascending. 

 The more common form is the fibrous root as seen 

 in grasses, the fibres being terminated by loose 

 cells or spongioles, which are the absorbent points. 

 But the main root is often thickened into a tap- 

 root, giving off secondary fibres globe-shaped, in 

 the turnip conical, or tapering gradually from the 

 collar to the attenuated fibre, in the carrot fusi- 

 form, or tapering at both ends, in the radish 

 abrupt, where the lower end appears as if cut 

 off, in the devil's bit scabious. In the dahlia, 

 the roots branch off in a fasciculate manner ; 

 while in the orchis (O. mascula) they are tuber- 

 ous, being in the form of globe-shaped bodies 

 filled with starchy matter. The so-called tuberous 

 roots of the potato are merely underground stems, 

 from the circumstance of their having eyes or buds 

 from which branches will spring. 



The crown, collar, or life-knot, as it is variously 

 called, is that part which lies between the stem and 

 the root It is the most essential portion of the 

 whole; for if it be removed, or seriously injured, 

 the plant will die ; whilst the small fibres or root- 

 lets, although an essential part of a plant, may be 

 destroyed at pleasure, so long as the crown re- 

 mains, for it readily reproduces them. When it is 

 of a slender make, it dries up as the seeds ripen, 

 and the plant soon dies, as seen in the corn-poppy, 

 mignonette, and other annuals. 



Roots have a remarkable tendency to grow down- 

 wards, or in the direction of the earth's centre ; and 

 from experiments, it seems not unlikely that this 

 tendency is to some extent an effect of gravitation. 

 The precise direction, however, is very much in- 

 fluenced by the condition of the soil. Both root 

 and rootlets extend as if in quest of food, and will 

 penetrate sidewise or obliquely to great distances. 

 Though the root and stem differ in many respects, 

 yet there are cases where it becomes difficult to dis- 

 tinguish between them. Some species of palms send 

 down aerial roots for the purpose of strengthening 

 their stems, and the same are seen very remarkably 

 in the screw-pines and banyans. Many herbaceous 

 plants send out roots in a similar manner when 

 they are earthed up ; and trees which grow in un- 

 natural situations, as on a wall or bare rock, send 

 down roots in quest of soil and moisture, which 

 afterwards take the appearance of stems. The 

 willow, maple, gooseberry, and some other plants, 

 may have their roots converted into stems by 

 reversing the plants, and burying the tips of the 

 shoots in the earth, so as to leave the roots in the 

 air. In this case, the branches will soon send out 

 fibrous roots from the joints which have been 

 buried in the earth, and the fibrous part of the old 

 roots withering, the roots themselves will gradually 

 assume the character of branches. 



The Stem. -When a plant shews itself above the 

 ground, it evidently manifests a strong tendency to 

 the light. Light, in fact, is essential in bringing it 

 to maturity, and in giving the green 

 colour to its leaves. The stem, with a 

 few exceptions, is always above ground. 

 It is divided from the root by the 

 part called the crown or collar. The 

 space between the collar and the first 

 branch is termed the bole or trunk 

 The stem of grasses, corn, and reeds, 

 receives the name of culm ; the stem of 

 such flowers as the primrose, dodeca- 

 theon (see fig.), and the daisy is undeveloped ; 



72 



hence they are called stemless (acaulescent) ; the 

 stalk upon which the flowers are borne being termed 

 the scape, or flower-stalk ; the running-stem, as in 

 the strawberry and cinquefoil, is termed a runner ; 

 a shorter runner that does not root, as in the house- 

 leek, is termed an offset; and a small stem pro- 

 ceeding laterally from a root or stool, a sucker. 



The stem assumes many forms and characters 

 as to bulk, structure, position, place, and dura- 

 tion. It appears as a corm (sword-lily, i) ; a 



bulb (the onion, 2) ; a culm (reed, 3) ; or as a 

 woody trunk (the oak, 4). When a trunk bears 

 permanent or perennial branches, the plant is 

 termed a tree; when permanent branches arise, 

 not from a distinct trunk, but from near the root, 

 the plant is termed a shrub ; and when the whole 

 stem is not woody, and dies down every year, at 

 least as far as the crown of the root, the plant is 

 termed a herb. Trunks which increase by suc- 

 cessive layers of new wood on the outside of the 

 old, as the ash and beech, are termed exogenous; 

 those which increase by the addition of fibrous 

 matter in the centre, as the palms, are styled 

 endogenous; and those which do not sensibly in- 

 crease in thickness, and are formed by the adhesion 

 of the leaf-stalks as they spring from the growing 

 point, as the tree-ferns, are said to be acrogenous. 

 (See SYSTEMATIC BOTANY, p. 108, figs, b, a.) 



Buds, which have various forms, consist of the 

 young shoots, leaves, or flowers, and proceed from 

 what is called the axil of a 

 leaf. They are usually formed 

 either early in summer or in 

 autumn, and are so con- 

 trived as to preserve from 

 injury the delicate structure 

 within. The outside is 

 composed of tough scales, 

 which are frequently cov- 

 ered with a gummy resin ; 

 and they are internally pro- 

 tected by a downy sub- 

 stance interposed between 

 the leaves. Linnaeus applied the term hylernacula 

 to leaf-buds, being the ' winter-quarters ' of the 

 young branch. With respect to the manner in 

 which the leaves are arranged and folded in the 

 bud, which is termed vernation, they may be 

 simply placed in apposition, as in the mistleto ; 

 plaited, as in the palm and birch ; doubled, as in 

 the rose and oak ; embracing, as in the iris and 

 the sage ; double embracing, as in valerian and 

 teasel ; rolled inwards, as in grasses ; rolled out- 

 wards, as in rosemary, primrose, &c. ; rolled 

 lengthwise, breadthwise, rolled from the tip to the 

 base, or wrapped round the stalk. 



