56 



HOW CROPS GROW. 



Fig. 10 represents an extremely thin slice from the stem of a cabbage, 

 magnified 230 diameters. The united walls of two cells are seen in sec- 

 tion at a, while at b an empty space is noticed. 



Fig. 10. 



The outer coating, or wall, of the cell is cellulose. This 

 substance is accordingly the skeleton or framework of the 

 plant, and the material that gives tough- 

 ness and solidity to its parts. Next to 

 water it is the most abundant body in 

 the vegetable world. 



All plants and all parts of all plants 

 contain cellulose, but it is relatively most 

 abundant in their stems and leaves. In 

 seeds it forms a large portion of the husk, 

 shell, or other outer coating, but in the 

 interior of the seed it exists in small 

 quantity. 



The fibers of cotton, (Fig. 11, <7,) hemp, 

 and flax, (Fig. 11, &,) and white cloth and 

 unsized paper made from these materials, 

 are nearly pure cellulose. 



The fibers of cotton, hemp, and flax, are simply 

 long and thick-walled cells, the appearance of 

 which, when highly magnified, is shown in fig. 

 11, where a represents the thinner, more soft, and collapsed cotton liber, 

 and frthe thicker and more durable liber of linen. 



