510 London Horticultural Society and Garden. 



The Position. With regard to this, Mr. Lindley observed that he had 

 already stated the fact, that both the root and stem of a bud or seed pro- 

 ceeded from one common centre ; which elongated itself at the same time 

 in opposite directions, the upper shoot producing the stem, and the lower 

 one the root. This was when the seed or bud was placed in its natural 

 position : if, however, it were reversed, and the part destined to produce 

 the stem were placed downwards, the tendency of the stem would still be 

 to ascend, and of the root to descend, in spite of the obstacles opposed to 

 this natural inclination. There is an extraordinary power possessed by 

 plants of accommodating themselves to circumstances ; and this power 

 was shown strongly in the case in question : the fibrils of the root might 

 be compelled by heat and moisture to germinate, and, finding no opening 

 in their natural direction, might be forced to expand upwards, but it was 

 only unwillingly and by mere compulsion ; and they would always be found 

 trying to overcome the difficulties opposed to their resuming their original 

 position. Many curious experiments have been tried with a view of ascer- 

 taining this fact, particularly by Du Hamel and several French physiolo- 

 gists. One of these experiments consisted in placing a bean, with the root 

 uppermost, in a bottle of water ; of which the bean exactly covered the 

 whole bottom, leaving no room below it. The root germinated, and, being 

 unable to insinuate itself between the bean and the glass, proceeded 

 upwards, but in a spiral manner, and making various efforts to find an 

 opening by which it could descend. Another experiment was, sowing buck 

 wheat on a surface of quicksilver ; and then, by means of heat and water, 

 forcing it to germinate : when the roots, being unable to penetrate the 

 quicksilver, ran along its surface, sometimes assuming a hooked appear- 

 ance, and, when near the edge of the pot, extending themselves over it, 

 and running down its sides. A third experiment was, filling a flower-pot 

 with fine, rich, moist earth ; and, having placed a seed close to the 

 bottom, suspending it in the air : the seed would soon begin to germinate, 

 but the root, instead of expanding itself in the nourishing soil prepared for 

 its reception, would turn over, and contrive, if possible, to force its way 

 out of the hole at the bottom of the pot into the open air, where, of 

 course, it must soon perish for want of moisture. It is a vulgar error to 

 suppose that the roots of a tree always extend as far as its branches. 

 That they do extend a considerable distance from the centre is certain ; 

 and it is a wise provision of nature that they do so ; as otherwise, from 

 the dense foliage of some trees keeping the rain from wetting the ground 

 for a considerable circle round their trunks, the roots, and consequently 

 the tree, would soon perish for want of moisture. 



The Structure of roots is essentially different from that of stems. Those 

 portions nearest the trunk of timber trees are, in fact, only elongated por- 

 tions of the stem, stretching into the ground for the purpose of giving sta- 

 bility to the trees. The roots necessary to vegetation are slender threads 

 called radicles, or fibrils, composed of fibrous tissue, embedded in cellular 

 substance; the centre of the fibres being abundantly provided with ducts, 

 for the. purpose of conveying the moisture extracted from the ground to 

 the plant. At the extremity of these fibrils is a portion of spongy mucus, 

 composed entirely of cellular tissue, and easily distinguishable to the 

 eye by its yellow tinge, as the professor demonstrated by exhibiting the 

 roots thrown out by the eye of a vine kept in water. The points of the 

 fibrils, as far as they are composed of mucus, are called the spongioles ; 

 and it is found, that, if they become dry, and lose their spongy qualities, 

 the tree must perish. They are, in fact, the mouths of the plant. 



The Growth of roots is different from that of stems. Stems increase by 

 the progressive developement of their parts, every bud containing within 

 itself the germ or embryo of the perfect plant : roots, on the contrary, 

 possess no power of self-elongation, but increase by successive depositions 



