BOOTS 27 



avoid the light, bear no leaves or buds, and are generally of a pale or 

 whitish colour although sometimes with coloured juice. 



' Functions. — The main function of the root is to obtain liquid food 

 from the soil. The tips of the root are chiefly concerned in this work, 

 the older portions merely serving as holdfasts for the plant, and as 

 channels for conveying the food to the stems and leaves. The 

 extremity of each root-fibre is covered with a cap, formerly called a 

 ' spongiole,' which protects a mass of young and active cells forming 

 the 'growing point.' As the roots push their way in a somewhat 

 corkscrew-like fashion through the soil, the outer layers of the root- 

 cap wear out and are replaced from within by the discarded layers 

 of the growing point. The contents of the cells of the growing point 

 are very sensitive to heat, cold, and moisture, and under favourable 

 conditions absorb water and whatever plant food is dissolved in it in 

 large quantities. During the spring and summer they are most active, 

 gradually subsiding towards autumn and becoming almost inactive in 

 winter. When plants are moved during the active state of growth 

 most of the root-tips are injured or broken, and the supply of food and 

 water is cut off from the plant until new roots are formed. Sometimes 

 plants moved at this period never recover from the shock to the roots 

 and, being unable to produce new ones quickly enough, die, practically 

 of starvation and drought. 



Many roots have root-hairs. These are developed chiefly on land 

 plants to assist in obtaining water more quickly from the soil. In 

 water-plants root-hairs are usually absent. But the roots of such 

 plants {e.g. the Watercress) grown on land soon develop root-hairs. 



From the above remarks it is obvious that one of the chief things 

 necessary to enable roots to perform their work properly is water. 

 Without moisture in the soil the roots are useless, and the entire plant 

 collapses in consequence. From a gardening point of view, therefore, 

 the greatest attention should be paid to the watering of plants, some 

 requiring more and some less, according to their nature. Whether the 

 water which is absorbed contains plant food or not depends a good 

 deal upon the operations of the gardener. It is possible that many of 

 the foods referred to at p. 70 are in the soil, but they must be readily 

 soluble in water, and also be in a fit state to benefit the plant. 



Besides the substances absorbed in the water, root-tips and hairs 

 absorb substances otherwise insoluble in water, and cling tenaciously 

 to particles of minerals. They exude an acid secretion which dissolves 

 the mineral matters, and these are thus modified so as to become 

 digestible, and readily pass through the cell-walls into the protoplasm 

 referred to above. 



