72 HOW CROPS GROW. 



tion of the flaxseed. The external cells, a, contain the mucilage. Whet 

 soaked in water, the mucilage swells, bursts the cells, and exudes. 



One or other of these kinds of gum has been found in 

 the following plants, viz., basswood, elm, apple, grape, 

 castor-oil bean, mangold, tea, sunflower, pepper, in various 

 sea-weeds, and in the seeds of wheat, rye, barley, oats, 

 maize, rice, buckwheat, and millet. 



In the bread-grains, Arabin, or at least a soluble gum, 

 occurs often in considerable proportion. 



TABLE OF THE PROPORTIONS (per cent) OP GUM IN VARIOUS AIR-DBI 

 PLANTS OR PARTS OF PLANTS. 



(According to VonBibra, Die Getreidearten und das Brod.) 



Wheat kernel 4.50 



Wheat flour, superfine 6.25 



Spelt flour, (Triticum spelta,) 2.48 



Wheat bran 8.85 



Spelt bran 12.52 



Rye kernel 4.10 



Rye flour 7.25 



Rye bnm 10.40 



Barley flour 6.33 



Barley bran 6.88 



Oat meal 3.50 



Rice flour 2.00 



Millet flour 10.60 



Maize meal 3.05 



Buckwheat flour 2.85 



The gums are converted into sugar by long boiling with 

 dilute acids. 



The recent experiments of Grouven show that, contrary 

 , to what has been taught hitherto, gum, (at least gum 

 Arabic,) is digestible by domestic animals. 



Saccharose or Cane Sugar, C 19 H 2Q O n , so called be 

 cause first and chiefly prepared from the 

 eugar cane, is the ordinary sugar of com 

 merce. When pure, it is a white solid, 

 readily soluble in water, forming a color- Fi g- 14 - 



kss, ropy, and intensely sweet solution. It crystallizes in 

 rhombic prisms, fig. 14, which are usually small, as in 



