SCIENCE PRIMERS. 



[VII. 



with such force does growth go on that it is common 

 to see stones of walls displaced by roots. In tropical 

 countries the destruction of buildings is universally 

 caused by the power of growing roots ; and neither 

 conquering nations, nor earthquakes, nor fires, nor 

 tempests, nor rain, nor all put together, have de- 

 stroyed so many works of man as have the roots 

 of plants, which have all insidiously begun their work 

 as slender fibres. 



44. Nourishment is taken in by the root-hairs, 

 but not by the growing-point. Root-hairs are delicate 

 long cells, that stand out from the surface of the 

 elongated radicle and of the root-fibres, and may be 

 seen on the first formed root of the pea and mustard 

 plants in great quantities. 



FIG. 14. Root-hairs, many times the real size. 



4.5. Roots may be roughly classed under two heads 

 those that simply nourish the plant as it grows, and 

 those that lay up a store of nourishment to assist the 

 growth of the plant during the second year. 



To the first class belong (a) the very simple annual 



