TEE DEPARTMENT OF AGRICULTURE 529 



Thus, the normal circulation is notably complete in woodlands, and is 

 notably deranged by deforestation; when the trees are felled and not 

 replaced by other cover transpiration ceases, the air dries so that seeds 

 and seedlings may wither, and the soil-water level lowers; the duff is 

 desiccated and wind-blown, leaving the previously porous soil to harden 

 and bake; and as storms arise the raindrops are no longer dashed into 

 spray by twigs and foliage and conveyed gently through litter and 

 natural mulch into a friable soil of enormous capacity for feeding 

 springs and brooks, but beat still harder the indurated ground — and 

 then gather in surface rivulets and rills running swiftly down the 

 slopes, eroding and gullying the soil on the way, clogging valleys with 

 the debris, and rushing as turbid torrents into the sea with little bene- 

 fit and large injury on their way. The Forest Service was created 

 largely to counteract reckless deforestation and maintain the timber 

 supply in certain sections of the country; yet it has grown into ad- 

 ministration of 170,000,000 acres of woodland, while its highest duty 

 has come to be that of acquiring and diffusing definite knowledge and 

 directing specific effort toward control over the powers of nature in 

 such manner as to protect the water supply and regulate that balance 

 of industries connected with woods and waters required for the com- 

 mon prosperity. The investigations extend into vegetal physiology 

 and the vital mechanism of the individual seed or slip or tree no less 

 than into the collective action and relations of the forest considered as 

 a unit, and pass over into both natural and artificial production. The 

 aim is increased efficiency of both individual trees and forests; the end 

 is higher national efficiency; the means, progressive control over nat- 

 ural powers through definite knowledge and purposive application. 



Over millions of acres of grass-lands and former woodlands, the 

 native flora is wholly or partly replaced by crop plants, and it is the 

 manifest destiny of all available lands to be consecrated wholly to pro- 

 duction or inhabitation or other human uses. In prehistoric times men 

 began to subsist on the products of the soil, and through unwitting 

 selection improved wheat and rye and barley and rice in the old world 

 and corn and beans in the new; and during the historical period the 

 improvement of the useful types and the replacement of Useless or 

 noxious types were continued under the guidance of increasing knowl- 

 edge. Since the Department of Agriculture was created — and largely 

 through its agency — the sum of human knowledge relating to crop 

 plants and their efficiency in this country has more than doubled; and 

 now the utility of plants is traced directly to individual vitality — to 

 the specific factors of cell function and reaction to stimuli and hered- 

 itary tendency combining with capacity for transpiration to determine 

 rate and limit of growth — which is itself measurably susceptible of 

 modification. In this way the Bureau of Plant Industry is steadily 



