50 BIOLOGY FOR BEGINNERS 



as in most grasses. In either case the soil particles are closely 

 held to the root by tiny root hairs, the active agents in absorption 

 which are adapted to take up the thin film of water that surrounds 

 all soil particles. 



While the form of the root system varies greatly, according to 

 the kind of plant, soil, and climate, yet, in general, all roots have a 

 very similar internal structure, as is shown by a study of sections 



FIG. 8. Section of corn root, showing root hairs formed from elongated 

 epidermal cells. From Atkinson. 



of roots in the laboratory. The tips of young roots, split length- 

 wise and dyed, so as to make their structure plain, should be used 

 for the purpose. 



Internal Structure. A typical root has a single outer layer, the 

 epidermis, composed of thin-walled, brick-shaped cells, from which 

 extend innumerable outgrowths called root hairs. Beneath the 

 epidermis is a thicker layer of thin- walled, loosely packed, roundish 



