The Eoot and the Soil. 



71 



Each root-hair consists of a single elongated cell (Fig. 



30), and is filled with protoplasm, as are the cells in other 

 living parts of the plant (13). As the ex- 

 tremity of the root advances through the soil 

 l by growth, new root-hairs are formed in front 

 of the older ones, while those farthest back as 

 rapidly die off, so that only a short portion of 

 a rootlet bears root-hairs at any one time. In 

 Fig. 27 root-hairs are visible in the left glass, 

 and in Fig. 6 they may be seen on the hypo- 

 cotyl of some of the germinating corn grains. 

 In Fig. 29A and in Fig. 28 the parts of the root 

 bearing root- hairs are indicated by the sand 

 which adheres to these parts. It is usually 

 difficult to see the root-hairs of plants grow- 



FiG.29. Seed- in & ln the natural Soil > but the y ma y SOme- 

 lings of turnip times be discovered with the help of a pocket 

 showing root- ma g n ifyi n g glass by carefully removing the 



iiiiirs. (Alter 



Frank and soil particles about the younger roots, when 



the silky network of root-hairs may be 



seen filling the smaller pores of the soil or enveloping 



the soil particles. Fig. 30 shows a magnified root- hair 



FIG. 30. Magnified root-hair of wheat, in contact with soil particles. 

 (After Sachs). 



of the wheat plant, closely attached to some particles of 

 soil. The root-hairs are able to take up water freely, 

 even from soil that does not appear very wet, because 

 each soil particle is enveloped in a thin layer of water 

 (91). Still more interesting 19 the fact, that root-hairs 



