130 AGRICULTURAL BOTANY 



As the thriftiness of a plant depends upon its root 

 branching, it is important to the farmer to know what 

 will induce the process. It has been found that trans- 

 planting, which consists in taking the plant from its 

 place and replanting it in another place, stimulates the 

 branching of roots. It is therefore beneficial to the 

 growth of the plant if done under proper conditions. It 

 is sometimes helpful to a plant to transplant it several 

 times in one season. 



Root pruning, or cutting off the root a few inches 

 below the surface, often stimulates the growth of 

 lateral branches, and if done to trees with a taproot, 

 like the walnut and hickory, the year before trans- 

 planting usually secures a sufficient growth of root- 

 lets to make transplanting successful. 



Plant Food through the Roots. Although it has 

 been stated that the root hairs cling tenaciously to 

 minute particles of soil, it must not be thought that 

 these particles ever enter the root of the plant. 



Root hairs take up as food only mineral matter held 

 in solution. Ordinary soil water contains a large 

 amount of this matter. How it passes into the root 

 to nourish the plant has been explained under osmosis. 

 The power of selecting just the mineral food the partic- 

 ular plant needs and rejecting all other seems to reside 

 in the protoplasm of the cell, but how the protoplasm 

 exercises this power is an unsolved mystery. The 

 protoplasm in the root hair of the barley, for instance, 

 will select a large proportion of silicon from the soil 

 water, while the protoplasm in the root hair of the 

 clover will take only a relatively small amount of the 

 same food, and yet both plants may be growing under 

 identical conditions. 



