CAUSES OF THE MOTION OF JUICES. 367 



plant is directed, now more to one class of proximate in- 

 gredients, as the carbohydrates, and now to another, as the 

 albuminoids, although the supplies of food presented are 

 uniform both in total and relative quantity. 



If a slice of red-beet be washed and put into water, the 

 pigment which gives it -color does not readily dissolve and 

 diffuse out of the cells, but the water remains colorless for 

 several days. The pigment is, however, soluble in water, 

 as is seen at once by crushing the beet, whereby the cells 

 are forcibly broken open and their contents displaced. 

 The cell-membranes of the uninjured root are thus appar- 

 ently able to withstand the solvent power of water upon 

 the pigment and to restrain the latter from diffusive mo- 

 tion. Upon subjecting the slice of beet to cold until it is 

 thoroughly frozen, and then placing it in warm water so 

 that it quickly thaws, the latter is immediately and deeply 

 tinged with red. The sudden thawing of the water with- 

 in the pores of the cell-membrane has in fact so altered 

 them, that they can no longer prevent the diffusive ten- 

 dency of the Digment. (Sachs.) 



Q 4. 

 MECHANICAL EFFECTS OF OSMOSE ON THE PLANT. 



The osmose of water from without into the cells of the 

 plant, whether occurring on the root-surface, in the buds, 

 or at any intermediate point where chemical changes are 

 going on, cannot fail to exercise a great mechanical influ- 

 ence on the phenomena of growth. Root-action, for ex- 

 ample, being, as we have seen, often sufficient to overcome 

 a considerable hydrostatic pressure, might naturally be 

 expected to accelerate the development of buds and young 

 foliage, especially since, as common observation shows, it 

 operates in perennial plants, as the maple and grape-vine, 

 most energetically at the season when the issue of foliage 

 takes place. Experiment demonstrates this to be the fact. 



