BOOT. 



RORQUAL. 



In many plant* the root*, instead of being covered with the capil- 

 lary fibre*. pment condensed membrane, which also inclones the 

 roots a* in a sheath, uid extend* to the point of the root where the 

 fibril* commence their growth. ThU structure occur* in moat water- 

 plauU, and in the root* of thoM pUnU which are accidentally pro- 

 jected into water, and in tome land-plant*. It drop* off with 

 Iranming age, in the same manner a* the root-hairs. It is aUo seen 

 in aerial plant*, a* the Ortkulacta. Mejen consider* this (heath a 

 modification of the root-bain, and hence infers that it performs the 

 me function*. (Mejen, ' Neue* System der Pflanzen-Phjsiologie,' 

 BaudiL) 



What the absorbent vessels are to the animal, the root* are to the 

 plant, and a difference between plant* and animal* ha* been pointed 

 out a* dependent on the relatire situation of their organs of absorption. 

 The animal derive* it* nutriment, by means of it* absorbent*, from an 

 internal reservoir, the stomach ; whilst the plant derives it* nutriment 

 from an external reservoir, the earth. The spongiole* of the root*, 

 a* we hare already stated, are the active agents in the absorption of 

 nutritious matter from the soil. By some botanist* it is supposed 

 that no other part of the root absorbs except the spongiole ; but from 

 the observation* of Meyen and other* it appears that the capillary 

 fibril* and the epidermis of the root have also the power of absorbing 

 fluid, though not in so high a degree a* the delicate point of newly- 

 developed tissue situated at the extremity of the fibrilla. [Ansonr- 



TIOX ; EXDOBM06IS.] 



Roots do not absorb everything that i* presented to them. It was 

 long ago ascertained by Davy that plant* did not absorb particles of 

 charcoal and other substance* that he diffused through water. 

 Experiment* also by Meyen, Link, and others, prove that the colour- 

 ing matter of various infusions is not taken up by the roots, and that 

 when this has been aupposeJ to have taken place, it has arisen from 

 m j.t.Ving a deposition of the colouring matter on the outside of the 

 tissue for an absorption into it 



When the root* of plant* are placed in solutions of gum, sugar, 

 starch, 4c., they thrive if the solutions are thin ; but if thick solu- 

 tion* of these substances be prepared, the plants die in them. Experi- 

 ment* of this kind were performed by Sir H. Davy, who attributed 

 the non-absorption of the thick solution, and the death of the plant, 

 to the blooking-up of the pores of the vegetable tissue by the thick 

 matter. 



When plant* are submitted to solutions of various poisonous agents, 

 they take up very varying proportions. De Saussure instituted a 

 series of very careful experiments for the purpose of ascertaining the 

 quantities of earthy and alkaline salts taken up by the roots of plants. 

 For this purpose he prepared solutions of the hydrochlorates, nitrates, 

 sulphates, and acetates of soda, potassa, and copper, and having sub- 

 mitted plant* of 1'olyyonum and liidtnt to them, he found that the 

 plants constantly absorbed a larger proportion of the water than of 

 the salt, and that the salt* were taken up in different proportions. 

 The salt* were not absorbed in proportion to their innocuous qualities, 

 as the sulphate of copper, which was the moat poisonous, was absorbed 

 in largest quantity. De Saussure concludes that it was not the 

 properties of the salts that determined their relative absorption, but 

 that it depended upon the relative consistence of the solutions. 

 I'lanta absorb poisons much more quickly when their roots are injured 

 by being torn or cut, and do not suffer much by exposure to weak 

 solutions of poisonous matters. This is a point of some practical 

 importance, and will explain how it is that vegetation does not suffer 

 when exposed to poisonous solutions. 



Another function which ha* been attributed to the roots U that of 

 excretion. Du Hamel first called the attention of botanists to this 

 subject ; he found that the root* of plants grown in water gave out 

 a brackish secretion, and looked upon it as a secretion from the fluids 

 of the plant Brugmans followed up this point, and, in conjunction 

 with Coulon, came to the conclusion, from the experiments they made, 

 that the secretion given out from the root* of plants was a process of 

 a similar nature to the rejection of the excrement* in animals, and 

 that these secretions acted beneficially iu the nutrition of some plants, 

 and injuriously in others. At the suggestion of De Candofle, M. 

 Macaira prosecuted some researches on this subject, which were pub- 

 lished in 1832 (' Mcmoires de U SocicUS de OdnSvre,' tome y., p. 287). 

 H* confirmed the view* of Bruitmaus and Coulon, and examined more 

 attentively the nature of the different excretions given out by plants 

 of different order*. Thus he found that the Lfgtunino$<t gave out a 

 gum and carbonate of lime ; Graminacea deposited a matter contain- 

 ing hydrochlorate* and carbonates of alkalies and earths, and contain- 

 ing but little gum ; Cickoractti, an abundant brown matter analogous 

 to opium ; K),l>orlnacta, a gum-resinous matter. It was inferred that 

 UMM excretion* were matters injurious to the plant, which were thus 

 thrown off from the system. This inference reemed to be confirmed 

 by an experiment of JCacaire's, in which, having divided the root* of 

 a plant of iltmriali* ammo into two parcels, he plunged the one 

 into a glass with solution of acetate of lead, and the other into a glass 

 of pure water ; iu a abort time it was found that the acetate of lead 

 had not only been teken up by the roots from the one glass, but that 

 it bad been excreted by them into the other. 



These researches were considered to offer a satisfactory explanation 

 of the practice of rotation of crops in agriculture ; the rotation being 



required on account of the excretion* of a plant being injurious to 

 iterlf, but beneficial to another, a* the excretion of one plant U the 

 food of another. [ROTATION or CHOPS, in ARTS AND So. D:v.] 



A far more rational explanation of the phenomena of rotation i* to 

 be found in the fact, that every plant requires certain inorganic 

 product*, a* well a* carbonic acid and ammonia, fur it* nutrition. 

 These inorganic matter* are supplied by the soil. When the same 

 plant i* grown for several years in succession in the same spot, it at 

 last exhausts the soil of the inorganic matters necessary to its growth. 

 By growing crops of another kind, and which do not require the same 

 constituents in the same soil, opportunity is given for the ingredient* 

 required by the first plant to accumulate in the soil 



It is now a well-known fact that certain plants will not grow with- 

 ont certain inorganic constituents. Thus the plants of the sea and 

 the sea-shore require chloride of sodium, but those which grow inland 

 demand the salt* of potash. The Onuses and Palms all require 

 silica wherewith to form their stems, and the Ctrtalianeed phosphatic 

 salt*. 



Just as these facts have become known, our agriculture ha* assumed 

 a more scientific character, and every farmer at the present day is 

 aware of the necessity of adding manures containing inorganic mat- 

 ters to his fields. It is on this account that Guano, Coprolites, and 

 the superphosphate of lime or materials containing it, are added so 

 constantly to the soil [QDANO; COPROLITES; PHOSFHATITK.] That 

 the necessity of rotation depends upon the exhaustion of these con- 

 stituents of the soil, is rendered also probable by the fact that some 

 soils grow the same crop continually for many years, which it may 

 be supposed depends upon an abundant supply of the inorganic con- 

 stituent* of the soil. Again, from recent experiments it has been 

 found, that by supplying artificially the inorganic food of plants to 

 the soil, that the same crop may be grown any number of years in 

 succession. 



It is upon a knowledge of the nature of the food of plants that all 

 agriculture must depend, and the principal source of this supply of 

 this food is the soil, and the organs which take up this food are the 

 roots. It is not however the chemical nature of the soil alone that 

 demands notice, but also it* physical properties. The great constituents 

 of the food of plants are carbonic acid, ammonia, and water, and these 

 are absorbed by the soil before they are supplied to the plant 

 According as the soil is capable of absorbing these constituents, will 

 depend to a considerable extent its power of growing all plants. It 

 is on this account that the absorbent nature of the soil in relation to 

 the important elements of the food of plants, should be inquired 

 into. The following table by Schubler of the absorbing power of 

 different substances in relation to water, will serve as an indication 

 of the importance of studying the physical properties of soils in 

 general (Schleiden, ' Principles of Scientific Botany ') : 



Besides the function of absorption, the root* serve other purposes 

 in the economy of the plant It U by means of the roots that a plant 

 maintain* its position in the earth ; and if for the increasing nourish- 

 ment of the plant an increase of the absorbing surface is required, it 

 is no leas necessary that, for the purpose of maintaining its stem 

 erect and firm, an extension of its holdfasts should take place. In 

 many instance* the root appear* to serve merely the purpose of holding 

 the plant in the ground, as in the mosses and many of the plants 

 belonging to the orders Crattulacta and Cactacett. By means of the 

 root* the temperature of plant* i* kept below that of the atmosphere 

 in summer, and above it in winter. This arise* from the root* absorb- 

 ing fluids from some depth below the surface of the earth, where its 

 temperature is not much affected by the changes in the atmosphere. 

 It is thus that the inhabitants of tropical climates are supplied with 

 fruits whose delicious juices, pumped up from the earth, are much 

 cooler than the atmosphere, and thus afford the most refreshing 

 articles of diet 



ROOT8TOCK. [STEM.] 



RORQUAL. 



