32 



Introduction to Botany. 



sorption and conduction of fluids, and storage. In follow- 

 ing the development of the seedling, we have noticed that 

 its first efforts are directed toward the formation of its root 

 system. It would be hazardous for seedlings to develop 

 .parts above the ground before an anchorage has been 

 made in the soil, for in that case the young plant could 

 easily be torn or washed from its position by storms, and 

 death would likely result from lack of water if the leaves 



were spread out above the 

 ground before connection 

 had been established with 

 the water of the soil. 



18. Growth of the Root.— 

 As shown by Experiments 

 41 and 49, the root, elongat- 

 ing only near the apex, is 

 directed downward by grav- 

 ity. The delicate root apex, 

 of course, meets with obstruc- 

 tions, but it is protected by 

 a cushion of cells known as 

 the root cap (see Fig. 10). 

 Being in a state of growth, 

 it is quickly responsive to 

 its surroundings, and, turn- 

 ing aside when it meets with 

 obstructions, it passes along 

 the course of least resist- 

 While the root is thus threading its way among the 

 soil particles, hairs are being formed on it, always a short 

 distance back of the apex, keeping pace with it as it 

 advances in growth and gradually dying off on the older 

 portions. Thus the root hairs, which are the main absorb- 



FlG. 10. 



Diagrammatic representation of a cross 

 and longitudinal section of a Root Tip. 

 K, a root hair ; m, a young lateral root ; 

 /, the root cap. Tracheal tubes are 

 shown near the center in both cross and 

 longitudinal section. Particles of soil are 

 represented clinging to the root hairs. 



ance. 



