398 BOARD OF AGRICULTURE 



Looking back through these periods of the earth's unwritten 

 history, we see how hopelessly these forms of life have struggled 

 against those disturbing forces which have altered the conditions 

 necessary to their existence. Variation in the development of the 

 surface of the earth necessitated a corresponding variation in 

 organic life. As the natural surroundings were favorable, one 

 group after another flourished and culminated, and as these became 

 less and less fitted to its wants, it gradually declined and finally 

 disappeared. 



It should here be remembered that we are not endeavoring to 

 show how far an organic type can change, but only to inquire if 

 it can change at all. If any modification can be demonstrated, 

 the extent of that modification will depend upon the power of the 

 modifying agent, and the nature of the circumstances under which 

 it is brought to act upon the organization. 



In the vegetable kingdom, the history of many of our cultivated 

 plants will afford us forcible illustrations upon this point. Of 

 those, perhaps none is more noticable than corn. Originally a 

 tropical grass, its disposition to yield to climate influence is very 

 elastic. In acceptable spots in southern latitudes, it attains a 

 height of from twelve to eighteen feet ; in a colder climate belt, 

 only two or three. 



In southern latitudes six or seven months are needed to briujr 

 it to maturity, while in colder climates it ripens in ninety days. 

 When cultivated for a series of years in a high and steady tem- 

 perature, it tends to revert to its original form of a succulent 

 grass. Its greatest productive value is on the Atlantic slope, in 

 about the latitude of 42°, while on the Pacific it seems disinclined 

 to mature its seed, though showing an average growth of stalk ; 

 thus exhibiting a wide contrast to wheat, which there attains its 

 maximum value. These are but a few of the many facts presented 

 by the wonderful flexibility of this plant under the modifying 

 agency of different climates. 



Wheat, though not so flexible in its disposition as corn, yet 

 shows a wide range of modification. The wi)iter and spring varie- 

 ties are mutually convertible in three years successive planting. 

 Coming to us iVom its ancient Asiatic home through Europe, it 

 brings with it the climate impress of that country, hence our Pacific 

 coast suits it better than the Atlantic, California producing the 

 finest variety in the world. Barley, near its northern limit of 

 production, will run the cycle of its life in ninety days ; in other 



