360 HOW CROPS GKOW. 



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

 imbibe 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' 



o 



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

 panding embryo. 



The quantity of water imbibed by the air-dry seed commonly amounts 

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

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

 plete in 48 or 72 hours, and was as follows in case of certain agricultural 

 plants : 



Per cent. 



Mustard 8.0 



Millet 25.0 



Maize 44.0 



Wheat 45.5 



Buckwheat 46.8 



Barley 48.2 



Turnip 51.0 



Rye 57.7 



Per cent. 



Oats 59.8 



Hemp s GO.O 



Kidney Bean 96.1 



Horse Bean 104.0 



Pea 106.8 



Clover 117.5 



Beet 120.5 



White Clover 126.7 



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. 



This^/fow proceeds in the ducts and intercommunicating 

 wood-cells. Between these and the soil intervenes loose 

 cell-tissue surrounded by a compactor 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 



