The Moot 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- 

 ti-cmity of the root advances through the soil 

 by growth, new root-hairs are formed in front 

 of the older ones, while those farthest back as 

 J^ rapidly die off, so that only a short portion of 

 ^1 a rootlet bears root-hairs at any one time. In 

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

 and in Pig. 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- 

 ing in the natural soil, but they may some- 

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

 showing root- magnifying glass by carefully removing the 

 Frank and soil particlcs about the younger roots, when 

 Tschirch). ^j^g silky network of root-hairs may be 

 seen filling the smaller pores of the soil or enveloping 

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



Fie. 29. Seed- 



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 is the fact, that root-hairs 



