70 



WATER AND MINERAL NUTRIENTS 



germinate radish or other seed, so that no delicate parts 

 of the root will be injured. For this purpose, place a few 

 seeds in packing-moss or in the folds of cloth or blotting- 

 paper, being careful to keep them 

 moist. In a few days the seed has 

 germinated, and the root has grown 

 an inch or two long. Notice that, 

 excepting at a distance of about a 

 quarter of an inch behind the tip, 

 the root is covered with minute 

 hairs (Figs. 11, 121). They are 

 actually hairs, that is, root-hairs. 

 Touch them and they collapse, they 

 are so delicate. Dip one of the plants in 

 water; remove it, — the hairs are not to be 

 seen. The water mats them together along 

 the root and they are no longer evident. 

 Root-hairs usually are destroyed when a 

 plant is pulled out of the soil, be it done 

 ever so carefully. They cling to the minute 

 particles of earth. Under a microscope, 

 observe how they are flattened when 

 they come in contact with grains of sand 

 (Chapter II). These root-hairs clothe the young rootlets, 

 and a great amount of soil is thus brought into actual con- 

 tact with the plant. Root-hairs are not young roots: they 

 soon die. 



148. Rootlet and root-hair differ. The rootlet is a compact, 

 cellular structure. The root-hair is a delicate tube (Fig. 

 122), within the cell-wall of which is contained living matter 

 (protoplasm); the wall and the lining membrane permit 

 water and substances in solution to pass in. Being long and 

 tube-like, these root-hairs are especially suited for taking 

 in the largest quantity of solutions; and they are the principal 

 means by which material is absorbed from the soil, although 



121. Root of pumpkin 

 seedling, showing the 

 covering of root-hairs. 



