96 PLANT LIFE ON THE FARM. 



mineral manures in addition in each case. Doubtless, 

 these characteristics are to be correlated with differences 

 of organization and structure, but with the exception 

 that the shallower rooted plants are often favored by 

 ammonia salts, and the deeper rooting ones by the more 

 deeply percolating nitrate, little or nothing has been done 

 in definitely associating the different physiological en- 

 dowments above referred to, with corresponding differ- 

 ences of internal structure. 



The LeguminoSft form a group of plants characterized, 

 so far as this country is concerned, by the presence of 

 "papilionaceous" flowers like those of the common pea, 

 by their leaves being compound, i. e., consisting of separ- 

 able segments, and by the production of a seed-pod, 

 which, when ripe, splits into two valves or flaps ; this is 

 technically called a " legume." By these characteristics, 

 not to mention others, this group which comprises peas, 

 beans, clovers, vetches, sainfoin, lucerne, and other agri- 

 cultural plants, may be known. Some, such as peas 

 and beans are annual, others are perennial, and, as a rule, 

 their habit or general appearance is so strikingly dif- 

 ferent from that of the grasses, that no one ever con- 

 founds them. 



Though containing a larger proportion of nitrogen in 

 their composition than the cereals, they are not specially 

 benefited by nitrogenous manures as the grasses are, and 

 this fact, observed when Leguminosas are grown alone, as 

 in the bean or clover field, is no less marked than it is 

 when they are grown in association as in pasture land. 

 At Kothamsted, the largest proportionate quantities of 

 Leguminosae occur on a plot to which mixed mineral 

 manure with potash is applied. Seasonal characteristics, 

 even when favorable to these plants, do not suffice to 

 overcome the injurious effects of some manures, as during 

 many years of varying character as to climate, they have 



