14 



ELEMENTS OP BOTANY. 



are surrounded by the moist soil and wrap themselves around 

 microscopical particles of earth. Thus they are able rapidly 

 to absorb through their thin walls the soil-water, with what- 

 ever mineral substances it has dissolved in it. 



18, The Root-Gap. — The tips of young roots and rootlets, 



Fig. 4. — Apparatus for Measurement) of Growth. 



as they bore their way through the soil, are protected from 

 injury by a coating of loose cells, called the root-cap, shown 

 at d in Fig. 3. It will be seen from this figure that no root- 

 hairs proceed from the root-cap, and indeed there is very 

 little absorption of water going on in this place. In the so- 



