[327J SCIENTIFIC MANUAL. 41 



hesion, manifested in capillary attraction, stimulated by 

 evaporation, and auxiliary to osmose; and vital force, which, 

 together with chemical action, produces the resultant veg- 

 etable organism, beginning with the germ of the seed, and 

 returning in annual cycles to the seed again. Osmose and 

 capillary forces supply the material ; vital force and chem- 

 ical action utilize them. 



Osmose is a general term applied to the interchange of 

 liquids of different densities through organic, membranous 

 partitions, and embraces both endosmose, the inward, and 

 exosmose, the outward flow of the liquid. 



Professor Gray says : 



44 / ndosmose and exosmose are names given by Dutrochet 

 (a French physiologist), to a physical process of permea- 

 tion and interchange, which takes place in fluids according 

 to the following law, briefly stated : When two liquids 

 of unequal density are separated by a permeable mem- 

 brane, the lighter liquid, or the weaker solution, will flow 

 into the denser or stronger, with a force proportioned to 

 the difference in density (endosmose) ; but, at the same 

 time, a smaller portion of the denser liquid will flow out 

 into the weaker (exosmose). 



4 * Thus, if the lower end ot an open tube closed with a 

 thin membrane, such as a piece of moistened bladder, be 

 introduced into a vessel of pure water, and a solution of 

 sugar in water be poured into the tube, the water from the 

 vessel will shortly be found to pass into the tube, so that 

 the column of liquid it contains will increase in height to 

 an extent proportionate to the strength of the solution. 

 At the same time, the water in the vessel will become 

 slightly sweet ; showing that a small quantity of syrup has 

 passed through the pores of the membrane into the water 

 without, while a much larger portion of water has entered 

 the tube. The water will continue to enter the tube, and 

 a small portion of the syrup to leave it, until the solution 

 is reduced to the same strength as the liquid without. 



' ' If the same solution be employed both in the vessel 



