CAUSES OF THE MOTION OF JUICES. 359 
ing the movements of the liquids of the plant is obvious. 
The cells and the tissues composed of cells furnish pre- 
cisely the conditions for the manifestation of motion by 
the imbibition of liquids and by simple diffusion, 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. Jmbibition 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. 
