THE LEGUMINOUS PLANTS. 59 



that wheat, for instance, will readily feed upon nitrogen in the 

 form of nitrates ; but if we apply nitrates to clover no effect is 

 produced. The wheat cannot take up the free nitrogen of 

 the air, but the clover can, through these root tubercles. 

 Sometimes clover does not grow well; and when pulled up 

 very few, if any, of these little tubercles are found upon the 

 roots. If, however, some soil in which clover has been growing 

 well, or the washing from such soil, is applied to the weak 

 clover, the plants soon begin to thrive and the tubercles are 

 seen growing upon the roots. These tubercles possess the 

 power of taking up free nitrogen from the air in the soil. If 

 we can get leguminous plants to grow in a poor soil and then 

 turn them under, they will decay and produce humus rich in 

 nitrogen that will give rise to nitrates (by nitrification) for the 

 benefit of the wheat or other grain crop that comes after. The 

 seeds from all leguminous plants are very rich. Then we can 

 state the following as the valuable points, in connection with 

 leguminous plants : 



1. They have many leaves and are good for fodder. 



2. Their seeds are very rich in food material. 



3. Their roots are generally long, therefore deep feeders. 



4. They take up free nitrogen from the air, and are therefore 

 easier on the soil than are cereals or root crops. 



PEAS are generally grown for the seed, which is very 

 rich in nitrogen and in oil. The many varieties grown for 

 man and stock are classed as garden peas and field peas. The 

 straw is richer than that of the grain crops. When grown to 

 be cut green for soiling, peas are generally sown with oats. 



BEANS are grown in this country for the seed, planted 

 in hills, as a garden crop, or as a field crop with good 

 garden cultivation. Some of the varieties, as the horse bean, 

 require a fairly mild climate. Some are short and bushy, 

 others are tall climbers. Examine their means of climbing. 



