94 PLANT LIFE ON THE FARM. 



Th^ grasses, both in number of species and in relative 

 and actual amount of produce, exceed the plants of all 

 other orders. The lowest produce occurs on the con- 

 tinuously unmanured plots ; the highest on those to 

 which a highly nitrogenous manure, such as ammonia 

 salts or nitrate of soda, is continuously applied in combi- 

 nation with earthy and alkaline salts especially potash. 

 But while the total gramineous produce is thus increased 

 by the description of manure just mentioned, the num- 

 ber of species of grass is reduced. On the unmanured 

 plots, on the average, sixteen different sorts of grasses 

 may be found, each contributing a fair proportion to the 

 total herbage ; thirteen only are found on the highly 

 ammoniated plots, and of these only a very few contribute 

 materially to the crop, the remainder being present in 

 such small quantities as to make but little difference in 

 the totals. 



The principal external characteristics which favor the 

 growth of the grasses in their competition with other 

 plants are their dense root-growth, monopolizing as it 

 were all the soil within reach, an$ affording little power 

 to the roots of other plants to penetrate the mass. To 

 an extent variable in different species, this root-growth 

 is both superficial as well as deep. In addition to this 

 generally ample root development, many of the species 

 are aided in the struggle by their stout tufted habit and 

 specially by their power of producing creeping offshoots 

 above or below ground which insinuate themselves in 

 between other plants and occupy any vacant territory. 

 No doubt internal anatomical differences are even of 

 greater moment than these external characteristics, but 

 these demand minute comparative study by means of the 

 microscope, under various conditions, and at different 

 seasons, and constitute a branch of inquiry at present 

 hardly even entered upon. 



Although grasses as a whole comport themselves in a 



