THE ROOTS OF PLANTS. 



Vi 



gamic because their sexual organs are concealed 

 or invisible ; they include ferns, mosses, lichens, 

 fungi, and algae ; they are a numerous class, and 

 comprehend nearly an eighth part of the 50,000 

 iinown vegetable productions. The following 

 table v^ill exhibit at one view tlie foregoing 

 statements : 



Organs of Nutrition, 



Organs of Reproduction, 



{Root. 

 Sti'vn, orfinchea. 

 Leavea 



rCalyx, corolla. 



Seamen. 

 i Pistil. 



Ovary. 

 LSeed. 



rMonocotyledouous— one seed 

 Division I. Phanprogamic, J lobe, as palms, grasses. 



or Flowering Plants, J Dicotyledonons — two seed 

 (. lobes, as oak, elm, bean. 



Division II. Cryptogamic,f^°"*y''*™''"'-<'«=«'»'« "' 

 or Nonflowering, | Ucheis '""' ' 



CHAP. V 



THE KOOTS 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 the 

 stem, that is, it descends perpendicularly, while 

 the other ascends into the atmosphere. Another 

 character of the root is, 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 

 vegetables 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 

 the water, having the roots immersed in it, but 

 not fixed, as the lemna 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 coufervte ; 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 fi'equently 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. Tlie 

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

 soil ; the other, usually proceeding from the 

 base of the leaves, are free and floating in the 

 midst of the water. The Clusia rosea, a shrub 

 of South America, the Sempermvimi arhor- 

 etim, the Indian corn, the mangrove, and some 

 species of figs, besides the roots which terminate 

 them below, produce others fi-om different points 

 of their stem, which often descend from a consid- 

 erable height and sink into the earth. These 

 have received the name of adventitious roots ; 

 and a remarkable fact respecting them is, that 

 they do not begin to grow in diameter tiU their 

 extremities have reached the soil, and drawn from 

 thence the materials of their growth. We must 

 not confound as roots certain subterraneous 

 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 pei-pendicular position, would be 

 almost sufficient to distinguish them fi-om 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 com'se 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 vrill push forward roots, 

 and thus become fixed in the earth. In grasses, 

 particularly in Indian com, the lower knots of 

 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 which is much 

 employed in horticulture. There is great ana- 

 logy of structure between the roots which a tree 

 shoots into the earth, and the branches which 

 it spreads out into the air. The principal dif- 

 ference between these twoorgans,depenclschiefly 

 on the different mediums in which they are de- 

 veloped. The roots of the gigantic Baobab tree 

 of Afi-ica, 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 fibres, while the latent buds of the 

 roots, which are destined annually to renew the 

 tufts of radical fibres, being placed in the other 

 medium are expanded into leaves. We have 



