cially at certain places, so changed, that the absorption is there 

 diminished and gradually disappears entirely. 



M. de Mirbel* has also in a few words treated of the struc- 

 ture of the terminal ends of the fibrils, and has controverted 

 the spongioles being peculiar organs of the apices of the roots. 



M. Dutrochet f has given in the complete edition of his 

 physiological works, a very valuable memoir on endosmosis, 

 which, from its highly important results, is of the greatest va- 

 lue to vegetable physiology. 



M. Dutrochet endeavoured in the first place to determine 

 what effect various degrees of temperature would have upon 

 the endosmosis of one and the same solution. The caecum of 

 a fowl was fixed to a glass tube, and this filled with a solution 

 of gum in 10 parts of water, and placed in distilled water, at 

 a temperature of 4 Reaum. ; the solution of gum had at- 

 tracted within 1J hour so much water that the apparatus in- 

 dicated an increase in weight of 13 .grains ; and in a water 

 at 25 to 26 the increase in the same space of time amounted 

 to 23 grains. In order to be able to give the results of such 

 observations with the greatest certainty, he constructed a pe- 

 culiar apparatus, which he calls Endosmometer ; by means of 

 this instrument the velocity of the endosmosis in various sub- 

 stances w r as measured, or rather the quantities of the fluid 

 which ascended in the endosmometer during a fixed time. 

 For instance, sugar-water of the specific gravity 1*047 at- 

 tracted in 1 hour so much water into the endosmometer, that 

 the instrument indicated 3^. On the other hand, a solution 

 of sugar of 1-258 spec. grav. indicated in the same time 19i. 

 The result of these experiments was this that the velocity of 

 the endosmosis produced by the various densities of the same 

 inner fluid, is in proportion to the excess of the density of the 

 inner fluid over the density of the exterior water. 



M. Dutrochet also determined by a series of experiments 

 the force with which the endosmosis takes place in various 

 substances, and at various densities of these substances ; 

 and it is the results of these experiments which are of such 

 importance to vegetable physiology. The apparatus with 



* L'Institut. 1837. p. 311. 



f M6moires pour servir a 1'histoire anatomique et physiologique des V6- 

 g^taux et des Animaux. A vec un Atlas de 30 planches. Paris, 1837. 2 vol. 



