CAUSES OP THE MOTION OF JUICES. 359 



ing the movements of the liquids of the plant is obvious. 

 The pells and the tissues composed of cells furnish pre- 

 cisely the conditions for the manifestation of motion by 

 the imbibition of liquids and by simple diifusion, as well as 

 by osmose. The constant disturbances needful to main- 

 tain constant motion are to be found in fully adequate de- 

 gree in the chemical changes that accompany the process- 

 es of nutrition. The substances that normally exist in the 

 vegetable cells are numerous, and they suffer remarkable 

 transformations both in chemical constitution and in physi- 

 cal properties. The rapidly diffusible salts that are pre- 

 sented to the plant by the soil, and the equally diffusible 

 sugar and organic acids that are generated in the leaf-cells, 

 are, in part, converted into the sluggish, soluble colloids, 

 soluble starch, dextrin, albumin, etc., or are deposited as 

 solid matters in the cells or upon their walls, Thus the 

 diffusible contents of the plant not only, but the mem- 

 branes which occasion and direct osmose, are subject to 

 perpetual alterations in their nature. More than this, the 

 plant grows ; new cells, new membranes, new proportions 

 of soluble and diffusible matters, are unceasingly brought 

 into existence. Imbibition in the cell-membranes and 

 their solid, colloid contents, Diffusion in the liquid con- 

 tents of the individual cells, and Osmose between the liq- 

 uids and dissolved matters and the membranes, or colloid 

 contents of the cells, must unavoidably take place. 



That we cannot follow the details of these kinds of ac- 

 tion in the plant does not invalidate the fact of their opera- 

 tion. The plant is so complicated and presents such a 

 number and variety of changes in its growth, that we can 

 never expect to understand all its mysteries. From what 

 has been briefly explained, we can comprehend some of 

 the more striking or obvious movements that proceed in 

 the vegetable organism. 



Absorption and Osmose in Germination. The absorp- 

 tion of water by the seed is the first step in Germination. 



