32 



PLANT GROWTH 



high and the leaf spread was thirty inches in diameter in 

 comparison with the root depth of five feet and root spread 

 of more than six feet. In such a plant the absorbing area of 

 the root system is considerably greater than the surface of 

 the shoot, through which the water is lost. 



Adventitious roots arise at any unusual place such as on 

 a vine or tomato stem that comes in contact with the soil. 



Fig. 8. The great extent of a maturing lima bean plant is shown. Two hundred 

 cubic feet of soil were ramified by the roots of a single plant. (From Weaver and 

 Bruner's Root Development of Vegetable Crops, McGraw-Hill Book Co., 1927.) 



Cuttings depend entirely on the development of adventitious 

 roots. In transplanting, should a large part of the normal 

 absorbing root system be destroyed adventitious roots will 

 develop. It is doubtful if adventitious roots are as success- 

 ful for plants as the normal ones, when distribution in the soil 

 and the union with the plant is considered in relation to the 

 growth of the mature plant. It must be noted, however, 

 that this question is not settled for all plants, and many 



