THE STEM. 



19 



cuan, jalap. The peculiar properties of roots, 

 however, shall be more fully described under 

 the heads of the pai-ticulai- plants used for 

 domestic and economical purposes. Certain 

 plants which have tlie power of shooting out 

 roots that ramify and extend to great distances, 

 are used for the purpose of consolidating sandy 

 and movable soils. Thus, in Holland, and 

 around Bourdeaux, the carex arenaria is planted 

 on the downs, and on the banks of canals, for the 

 purpose of fixing and consolidating the soU; and 

 the saUow thorn, and Spanish broom, are used 

 in many other countries for similar purposes. 



CHAP. VI. 



THE STEM. 



As the root tends towards the earth, so the 

 stem is that part of the plant which mounts into 

 the atmosphere, and besides giving support, 

 and the means of attachment, to leaves, blossoms 

 and fruit, it contains also the vessels which 

 convey the sap from the root upwards. Some of 

 the simpler plants have 

 no stem, as the lichens; 

 others have a soft herba- 

 ceous mass, in which are 

 combined stem, branches, 

 and leaves, as the duck 

 weed or lemna, already 

 alluded to, the cactus, &c. 

 In the fungi, the nature 

 of the stem a b, is simple, 

 and composed of the same 

 cellular membrane as the other parts of the plant. 



AU the phanerogamous, or flowering vege- 

 tables, have a proper stem, but this stem, in many 

 species, is so small as to be occasionally over- 

 looked ; of this kind are the primrose and hya- 

 cinth, the leaves of these plants appearing as if 

 they sprung directly from the summit of the 

 root. In these last mentioned plants, and many 

 others, there is a stem which shoots up, and 

 bears the flowers and seed; this is called the 

 scape, and is not to be confounded with the 

 true stem. Sometimes this flower stalk springs 

 from a part of the leaf of the plant, when it is 

 called the radicle peduncle, as in the plantain. 

 There are several kinds of stems, which we shall 

 proceed to notice. 



77te trunk is the central and supporting part 

 of trees, as the oak, ash, fir. Its largest diameter 

 is at the root, and it tapers gradually as it 

 ascends, assuming somewhat of a conical form. 

 For a space below, it is single and naked, but as 

 it approaches the top it divides and subdivides 

 into numerous ramifications; on these branches, 

 twigs, and ramuli, are situated the leaves, blos- 



soms, fruits, seeds. The tmnk is peculiar to 

 dicotyledonous trees ; internally, it is made up 

 of successive circles of woody matter, disposed 

 one inside the other in conqpntric layers, and 

 increases in height and breadth by the addition 

 of new layers, formed one outside the other like 

 a succession of cones. 



The stipe is the stem of the monocotyledonous 

 class of trees, such as the palms and yuccse, and a 

 few of the dicotyledonous, as the cycas and zamia. 

 It is a cylinder of equal thickness from top to 

 bottom, sometimes even swelling out in the 

 middle or the top, with no branches, but crowned 

 at the summit by a tuft of leaves and flowers. 

 Its bark differs little in structure from the stem. 

 It increases in height by the successive growths 

 of the bud at the top, and in breadth by the 

 multiplication of its filaments. Internally, its 

 structure also differs from that of the dicotyle- 

 donous ti'unks. 



77;e culm, er straw, is the supporting stem of 

 the grains, grasses, reeds, and canes. It is a 

 simple or single stem, rarely branched, most 

 commonly hoUow within ; and having at inter- 

 vals knots or compressed parts, which give it 

 strength and soUdity, and from which proceed 

 alternate leaves. 



The stock or rhizoma, or stem root, as it has 

 been called, is found in a considerable number 

 of plants. It is partly or entirely concealed 

 under ground, is irregularly knotted, and sends 

 off new stems from its anterior part, as the others 

 decay. Of this kind, are the stems of the iris, 

 scabiosa, anemone, and Solomon's seal. See wood 

 Cut. Besides, its nearly horizontal direction 

 under ground, one of the principal characters of 

 the stock, and by which it is distinguished fi'om 

 the root, is that it always, in some part of its 

 extent, presents traces of the leaves of preced- 

 ing years, or scales which take place of them, 

 and that it increases by its base, or the part 

 nearest the leaves which is the reverse of what 

 takes places in the true root. 



The general name of stem is given to all those 

 varieties which do not strictly come under any 

 of the above descriptions; and it may be re- 

 marked, that the number of vegetables that have 

 a proper stem, is much greater than that of those 

 with a stipe, or culm, or trunk. The practical 

 Botanist distinguishes the varieties of the stem 

 thus : — 



Herbaceous, green, tender, and lasting for a 

 single year ; as borage, chickweed, camfrey, &c. 

 All these rank under the name of herbs. 



Semiligneous, half woody, hard, and continues 

 above ground for several years, while the slender 

 twigs and branches are removed annually; as 

 common rue, garden thyme, sage. 



Woody (ligneous) stem, hard, solid, enduring 

 for years; divided into two classes. Shrtiis, 

 which send out branches from the base or root. 



