360 HOW CROPS GROW. 



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

 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 

 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. R. Hoffmann has made observations 

 on this subject, (Vs. /SY., 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 35.0 



Maize 44.0 



Wheat 45.5 



Buckwheat 46.8 



Barley 48.2 



Turnip 51.0 



Rye 57.7 



Per cent. 



Oats 59.8 



Hemp 60.0 



Kidney Bean 96.1 



Horse Beau 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. 



TliisJZow 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 

 train nccess to tlio ducts. The latter are formed in young 



