A history of the vegetable kingdom. Embracing the physiology, classification, and culture of plants, with their uses to man and the lower animals, and their application in the arts, manufactures, and domestic ecomony / By William Rhind.

  • Rhind, William, active 1818-1867.
Date:
[1840?]
Catalogue details

Licence: Public Domain Mark

Credit: A history of the vegetable kingdom. Embracing the physiology, classification, and culture of plants, with their uses to man and the lower animals, and their application in the arts, manufactures, and domestic ecomony / By William Rhind. Source: Wellcome Collection.

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    and very close, as in the heaths. The internal structure of roots very closely resembles that of the stem, and shall he described along with that organ. According to the general laws of vegetable growth, plants of the same species are furnished with the same species of root, not producing at one time a woody or fibrous root, and at another a bulbous root. Yet some exceptions to this rule occur. If part of the root of a tree planted by a pond or river, is accidentally laid bare on the side next the water, or > if in the regular course of its growth it protrudes beyond the bank, so as to be now par¬ tially immersed, the future de¬ velopment of the part is considerably affected; for the root, which was formerly firm and woody, instead of augmenting in the regular way by the accession of new layers between the wood and bark, thus enlarging the mass, divides now at the extremity into many ramifications, or sends out a number of fibres from the surface, which become again subdivided into fibres still more minute, and gives to the whole an appear¬ ance something like a fox’s tail. This may be seen in willows, growing beside ponds. On the other hand, the phleirn pratense, when growing in its natural moist soil, has a fibrous root; but when in a dry soil, where it is not unfrequently found, the root is bulbous. The roots of utricularia minor, exhibit curious appendages of small membranous bladders attached to their slender filaments, containing a transparent fluid and a bubble of air, by means of which the plant is kept floating in the water. If a slice of the beet root be examined when the plant is a year old, it will exhibit from five to eight concentric circles of tubes or sap vessels, imbedded at regular in¬ tervals in its pulp ; whereas other biennial roots form only one circle for each year, and are con¬ sequently furnished at no time with more than two. The most singular circumstance regarding roots, however, is that they may be transformed into stems, by inverting the plant. Thus, if the stem of a young plum or cherry tree, or of a willow, is taken in autumn, and bent so as that one half of the top may be laid in the earth, one half of the root being at the same time taken carefully out, but sheltered at first from the cold, and then gradually exposed to it; and the remaining part of the top and root subjected to the same process in the following year, the branches of the top will become roots, and the ramifications of the root will become branches, protruding leaves, flowers, and fruit in their season. Use of roots. In the first place, as regards the plant itself, the use of the roots is to serve as a means of attachment to it in the soil, and to draw from thence a portion of the juices necessary for its life and nourishment. The roots of many plants appear to perform only the first of these functions. This is chiefly re¬ markable in thick succulent plants, which ab¬ sorb from the air the substances necessary for their nutrition at all points of their surface ; in this case, these roots serve simply to fix the plants to the soil. The magnificent cactus Peruvianus, growing in the hot house of the museum of natural history at Paris, is of an extraordinary height, and sends out its large branches with extreme vigour, and often with amazing rapidity; yet its roots are contained in a box which barely holds four cubic feet of earth, which is never re¬ renewed or watered. Some other plants of the same nature may be suspended by a thread to the ceiling, and they will grow without any earth at all, merely by absorbing their nourishment from the atmosphere. Neither are the roots of plants always in proportion to the strength or size of the trunks which they support. The tribe of palms and pines, whose trunks sometimes reach the height of a hundred feet and upwards, have very short roots, vdiich do not extend far in the ground, and attach themselves but feebly to it. On the contrary, herbaceous plants, whose weak and slender stems die yearly, have sometimes roots of great length and size compared with the stem, as is the case in the liquorice shrub, lucern, and the common weed called rest-harrovr. In general, however, roots extract from the earth the substances which contribute to the growth of the plant. All parts of the root, however, do not equally perform this office, which is accomplished chiefly, if not solely, by the ex¬ tremities of the small fibres. It has been found that their extremities are terminated by little spongy bodies, called ampullce or spongioles, with porous absorbing mouths. Dutrochet has min¬ utely described these spongioles, vdiich may be seen by the aid of a microscope, attached as little bags or knobs, to the minute fibres of the roots, as seen at a a in the vrood cut. With a high magnifying power, hexagonal cells are visible, covered by a porous cuticle. The small bulb at the extremity of the root of the common duck weed, affords a good example of these spongioles. Whatever be their structure, Dutrochet thinks, ab¬ sorption is performed by those extremities alone; and the truth of this may be established by a simple experiment. If we take a radish or turnip, and immerse in water the small root by which the bulb is terminated, it will vegetate and shoot forth leaves. On the contrary, if it be so placed in the wrater that its lowTer extremity is not immersed, it gives no 21.