102 



So readily does the cow pea grow upon many soils which 

 fail to respond to the requirements of other crops, that 

 when it is desired to convey the idea of an almost total lack 

 of fertility in a soil, we often hear the expression —"the land 

 is too poor to grow cow peas." 



It was formerly supposed that this capacity of collecting 

 plant food so successfully, even on very poor soils, was due 

 to the long and deep reaching roots which were presumed 

 to readily take up supplies of plant food beyond the reach 

 of many other crops. The amounts of nitrogen assimilated 

 by the pea and similar plants on rather unfertile soils were 

 frequently so out of proportion to the available supplies of ni- 

 trogen iu these soils, that investigators have for years sought 

 to determine whether or not these plants possessed the 

 power of assimilating the free nitrogen of the atmosphere. 

 The researches and experiments of a number of German in- 

 vestigators, extending over a long period of years, have at 

 last shown that leguminous plants are capable of taking up 

 and assimilating the nitrogen of the atmosphere, and this 

 property is known to be dependent upon the presence of 

 bacteria or minute microscopic forms of life, which are 

 found in the tubercles or excrescences which occur quite 

 profusely upon the roots of thrifty and vigorous plants of 

 this character. 



Certain particular bacteria are found to be peculiar to cer- 

 tain specific plants, and plants grown in a soil destitute of the 

 organism peculiar to them, are observed to have few if any 

 root tubercles. ^» 



By adding to the soil in question small amounts of soil 

 from land on which similar plants are observed to develop 

 root tubercles, it will be found that the plants grown on the 

 former soil will also soon have tubercles formed upon their 

 roots, and at the same time, the growth of the plants be- 

 comes vigorous and rapid. The presence of these bacteria 

 in the tubercles of the roots of leguminous plants, in con- 

 nection with the functions which the bacteria perform, con- 

 stitutes an example of what is termed by scientists "sijm- 

 hiosis" {life together), the plant, itself, and these micro-organ- 



