THE ROOTS OF PLANTS. 



K 



painic because their sexual organs are concealed 

 or invisible ; they include ferns, mosses, lichens, 

 funpfi, and aljja; ; they are a numerous clfvss, and 

 comprehend nearly an eightli part of the 50,000 

 IcnowTi vegetable productions. The following 

 table will exhibit at one view tlie foregoing 

 statements : 



Organs of Nutrition, 



{Root. 

 Stem, DrancliPft. 

 Leaves. 



fCfilyx. corolla. 



iSriunt'ii. 

 Pistil. 

 Ovary. 

 Seed. 



CM'inoeotyledonous— onp seed 

 Division L Phanerogamic, J lobe, a^ palms, grasses, 

 or Flowering Plants, J Dicotyledonous — two seed 

 (, lo'jes, as oak, elm, beau. 



Division II, CrvptogamicfAcotyled.raons- destitute of 

 or Nouflowering, [ seed lobes, as mosses, fenis. 



CllAP. V. 



TUE UOOTS OP PLANTS. 



The root is that part of the plant which, 

 forming its lower extremity, is almost always 

 concealed in the earth, and which grows con- 

 stantly in a direction opposite to that of tlie 

 stem, that is, it descends perpendicularly, while 

 the other ascends into the atmosphere. Another 

 character of the root in, that it never turns green, 

 at least in its tissue, when exposed to the action 

 of air and light ; whereas all the other parts of 

 ■v'pgetables acquire that colour when exposed. 

 This definition is perhaps as comprehensive as 

 any that can be given, whether with regard to 

 the class of perfect or imperfect plants, though 

 it is no doubt liable to many exceptions, if ap- 

 plied to both. For even of plants denominated 

 perfect, some are found to float on the surface of 

 tiie water, having the roots immersed in it, but 

 not li.ved, as the Icmna or duck weed ; and of 

 plants of a still simpler structure, some have no 

 root at all, or at least no visible part distinct from 

 the rest, to which that appellation can be as- 

 cribed, such as many of the conferva; ; or they, 

 are apparently altogether root, as the truffle. 

 There are also many of the simpler plants which 

 attach themselves to other vegetables, and to 

 various substances from which they cannot be 

 supposed to derive any sort of nourishment 

 whatever, owing either to the mode of their at- 

 tachment, or to the character of the substances 

 to which they attach themselves. Such are 

 many of the mosses, lichens, and marine plants, 

 found adhering to the outer and indurated bark 

 of aged trees, to dead or decayed stumps, to 

 rotten pieces of wood, and iiequently even to 

 stones. These, therefore, are to be regarded as 

 exceptions to the rule. Most aquatic plants, 



such as the buck bean, water lily, hooded mil- 

 foil, are possessed of two kinds of roots. 'J'hc 

 one, sunk in the earth, fix the plant to the 

 soil ; the other, usually proceeding from tlie 

 base of the leaves, are free and floating in the 

 midst of the water. The Chisia rosea, a shrub 

 of South America, the Sempervivum arbor- 

 cum, the Indian corn, the mangrove, and some 

 species of figs, liesides the roots which terminate 

 them below, produce others from different points 

 of their stem, which often descend from a consid- 

 erable height and sink into the earth. Tiiesc 

 have received the name of adventitious roots ; 

 and a remarkable fact respecting them is, that 

 they do not begin to grow in diameter till their 

 extremities have reached the soil, and drawn from 

 thence the materials of their growth. We must 

 not confound as roots certain subteiTaneous 

 stems of vegetables which creep horizontally 

 under the soil, as in the German Iris, Solomon's 

 Seal, &c. The direction of these alone in a 

 horizontal, not perpendicular position, would be 

 almost sufficient to distinguish them from the 

 true roots if other characters did not mark them. 

 Different parts of vegetables are capable of pro- 

 ducing roots. Cut off a willow branch, or the 

 branch of a poplar, plant it in the earth, and in 

 the course of a short time its lower extremity 

 will be covered with rootlets. The same will 

 happen when both extremities are planted in 

 the soil ; each of them will push forward roots, 

 and tlius become fixed in the earth. In grasses, 

 particularly in Indian corn, the lower knots ot 

 the stem sometimes give out roots, which de- 

 scend and sink into the earth. It is on this 

 property of the stem, and even of the leaves of 

 many vegetables, of producing new roots, that is 

 founded the practice of propagating by slips and 

 layers, a means of multiplication whicli is much 

 employed in horticulture. There is great ana- 

 logy of structure between the roots whicli a tree 

 shoots into the earth, and the branches which 

 it spreads out into the air. The principal dif- 

 ference between these twoorgan3,depeni1schicfly 

 on the different mediums in which they are de- 

 veloped. The roots of the gigantic Baobab tree 

 of Africa, are said to extend one hundred feet 

 in length. It has been said, that when a young 

 tree is inverted so as to have its branches buried 

 in the earth, and its roots in the air, the leaves 

 are changed into roots and the roots into leaves. 

 This, however, is incorrect ; the leaves are no 

 more changed into roots than the roots into 

 leaves. But when they are placed under the 

 earth, the buds situated in the axilla of the 

 leaves, instead of producing young branches, or 

 leafy scions, are elongated, blanched, and become 

 radical filn-cs, Avhilo the latent buds of the 

 roots, which are destined annually to renew the 

 tufts of radical fibres, being placed in the other 

 medium are expmded into leaves. We have 



