360 



HOW CEOPS GROW. 



The coats of the dry seed when put into the moist soil 

 imhibe this liquid which follows the cell-walls, from cell 

 to cell, until these membranes are saturated and swollen. 

 At the same time these membranes occasion or permit os- 

 mose into the cell-cavities, which, dry before, become dis- 

 tended with liquid. The soluble contents of the cells or 

 the soluble results of the transformation of their organized 

 matters, diffuse from cell to cell in their passage to the ex- 

 panding embryo. 



The quantity of water imbibed by the aiv-cliy seed commonly amounts 

 to 50 and may exceed 100 per cent. K. HofTmann has made observations 

 on this subject, (Fs. St., VII, p. 50.) The absorption was usually com- 

 plete in 48 or 73 Bours, and was as follows in case of certain agricultural 

 plants : — 



Fer cent. Fer cent. 



Mustard 8.0 



Millet 35.0 



Maiize 44.0 



AVheat... 45.5 



Buckwheat 46.8 



Barley 48.3 



Turnip 51.0 



Eye 57.7 



Oats 59.8 



Hemp 60.0 



Kidney Bean 96.1 



Horse Bean 1010 



Pea 106.8 



Clover 117.5 



Beet 130.5 



White Clover 136.7 



Root- Action. — Absorption at the roots is unquestiona- 

 bly an osmotic action exercised by the membrane that 

 bounds the young rootlets and root-hairs externally. In 

 principle it does not differ from the absorption of water 

 by the seed. The mode in which it occasions the surpris- 

 ing phenomena of bleeding or rapid flow of sap from a 

 wound on the trunk or larger roots is doubtless essentially 

 as Hofmeister first elucidated by experiment. 



Tbis^ow proceeds in the ducts and intercommunicating 

 wood-cells. Between these and the soil intervenes loose 

 cell-tissue surrounded by a compacter epidermis. Osmose 

 takes place in the epidermis with such energy as not only 

 to distend to its utmost the cell-tissue, but to cause the 

 water of the cells to filter through their walls, and thus 

 gain access to the ducts. The latter are formed in young 



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