ABSORPTION. 



in the branches placed in an inverse direc- j 

 tion ; secondly, from the observation of com- 1 

 mon gardeners, and of Mr. T. A. Knight, that, 

 in the cuttings made in an inverse manner, it 

 is more frequently only the lower buds which 

 are developed, and not the higher ones, as 

 happens in those made in a direct manner. It 

 is necessary, in order to render these experi- 

 ments comparative, that the horizontal cuttings 

 be made equal ; and, as we were doubtful 

 whether this circumstance had been taken into 

 consideration, we made the following experi- 

 ment : We placed two branches of willow in 

 water, the one in a direct manner, the other 

 inverted, and contrived in such a manner that 

 these two absorbing bodies were equal ; but 

 the branch which was placed inverted pushed 

 its roots a little slower than the direct one. 

 (Mem. sur les Lentictlles, Ann. des Sc. Nat., 1825, 

 Jan., pp. 18, 19.) 



The wood tends not only to absorb the water 

 by its transverse section, but also lengthways. 

 Thus we placed in water (ibid., p. 4) a branch 

 of willow, the section of which was covered 

 with mastic, but which had the part immersed 

 denuded of the bark by taking off a cortical 

 ring of an inch in length. This branch pushed 

 its buds and roots in a manner similar to the 

 branches which are immersed by a transverse 

 section. 



The hygrometrical power of wood is such 

 that when we expose it to the air it easily im- 

 bibes fhe surrounding moisture; and, when 

 preserved in shady places, it never dries of 

 itself. Count Rumford (Mem. sur k Buis et h 

 Charbon: 8vo, Paris, 1812) dried in an oven a 

 piece of wood taken from the interior of a 

 beam which had been placed for one hundred 

 and fifty years in a battlement, and observed 

 that it lost about ten per cent, of its own 

 weight; and he thinks that this is the greatest 

 degree of natural desiccation which wood can 

 attain in our climate. An oak faggot, exposed 

 eighteen months in the air, and which might 

 be regarded as excellent wood for burning, lost 

 twenty-four per cent. The same experimenter 

 observed that, when chips of wood have been 

 well dried in a stove, on their exposure to the 

 open air they very freely imbibe water. If 

 these chips are placed for twenty-four hours in 

 a room, the extremes of this power of absorp- 

 tion have proved to be, on one side, the Lom- 

 bardy poplar, whose chips, five inches long by 

 six lines broad, have sucked up 0-87 grains ; 

 and, on the other, a billet of oak of the same 

 dimensions, which sucked up 1-40 grains. 

 When the same chips were exposed for eight 

 successive days, it was found that they did not 

 increase in weight if the air had remained at 

 the .same temperature, but they lost in weight 

 if the air became more heated. This experi- 

 ment, then, proves that the absorption is rapid; 

 and that the equilibrium it attains will be 

 determined by the surrounding atmosphere, 

 anA certainly also by its own hygrometrical 

 polfer. 



These necessary conditions of existence 



have been effected by the organization of the 



spongelets as organs of suction, and by the 



nature of the water, which is abundantly dif- 



14 



ABSORPTION. 



fused over nature, and also impregnated with 

 their principal nourishment. 



The nature of the action of the spongelets is 

 remarkable in this, that the choice which they 

 seem to make of the matter which they absorb 

 does not appear to be determined by the na- 

 tural wants of the plant, but the facility is less 

 or more influenced by the nature of the liquids. 

 Thus, M. Theodore de Saussure (Rech. Chirn., 

 ch. 8) found, that if we place plants in water, 

 with which is mixed sugar, gum, or the like, 

 the spongelets will absorb a greater proportion 

 of water than of the materials which are dis- 

 solved in it; for the water which remained 

 after the experiment was more saturated than 

 before the roots were put into it. Again, if we 

 plunge the roots into different solutions, they 

 will absorb so much the more of these in pro- 

 portion to their fluidity, although at the same 

 time such solutions may be injurious to the 

 plant, and yet will they absorb a less propor- 

 tion of viscous matter, although this may con- 

 tain more nutritive materials. Thus, of blue 

 vitriol (sulphate of copper), the most hurtful 

 of the substances employed, they absorbed a 

 large quantity, but a very small quantity of the 

 gum, which is not injurious. When we placed 

 plants in solutions of gum, of different degrees 

 of thickness, we found that the quantity absorb- 

 ed was smaller in proportion as the solution 

 was more viscous. Sir H. Davy, also, observed 

 that plants perished in those solutions in which 

 there was a large quantity of sugar or gum ; and 

 prospered when the solutions had only a small 

 quantity of either. (Agricultural Chem.) 



The effect of the viscosity is obviated when 

 we put the roots in water which holds organic 

 matters in suspension. Thus, the drainings 

 of dunghills, and impure waters, are taken up 

 by the roots in smaller quantities than pure 

 water. It should seem that these particles 

 have a tendency to obstruct the imperceptible 

 pores, passages, or cells of the spongelets. M. 

 Th. de Saussure remarks that analogous laws 

 may be observed in the case of liquids in 

 which different substances are dissolved, the 

 more fluid being absorbed in a greater quan- 

 tity than others. It would accordingly appear 

 that the roots exercise a kind of choice in the 

 soil ; but that the choice, far from being relative 

 to the wants of the plants, is a circumstance 

 purely mechanical. 



On the other hand, M. Pollini, who has 

 repeated these experiments, found that of the 

 solutions of different substances in water, the 

 roots sucked up different quantities, without 

 any apparent regard to their viscosity. Thus 

 he constantly found, he says, that the roots 

 absorbed more of common salt, or of potass, 

 than of the acetate or of the nitrate of lime, 

 and more of sugar than of gum. He found, on 

 the other hand, that if he cut the extremity of a 

 root, the water which entered by the wound 

 contained indifferently all the salts which had 

 been dissolved in the water ; and the portion 

 which remained after absorption did not con- 

 tain more than before. (Suggin di Osserv. e di 

 Sperienze sulla Veget. degli Albert : Verona, 

 1815.) 



Another circumstance remarkable in the 



