72 AGRICTJLTUEAL PEODUCTS OF THE UNITED STATES. 



Agricultural Products of the United States. 



According to the census of 18T0, tlie United States had, on the 

 first of June in that year, in round numbers, 189,000,000 acres of 

 improved land,"^ the quantity haviag been increased by 16,000,000 

 acres within the ten years next preceding. In 1880 the number 

 of acres of improved land was 284,721,012, showing an increase 

 during the last decade of nearly 96,000,000. Not to mention less 

 important crops, this land produced in 1879, in round numbers, 

 460,000,000 bushels of wheat, 20,000,000 bushels of rye, 408,- 

 000,000 bushels of oats, nearly 10,000,000 bushels of pease and 

 beans, 44,000,000 bushels of barley, orchard fruits to the value 



whether weeds have any common characteristic which may give them advan- 

 tage, and why most of the weeds of the United States, and probably of similar 

 temperate countries, should be foreigners. This latter is strikingly the case on 

 the Atlantic side of temperate North America, where the weeds have mainly 

 come from Europe, and the common answer to the question must be largely 

 true — viz., that as the region was not really forest clad, there were few of its 

 native herbs which, if they could bear the exposure at all, could compete on 

 cleared land with emigrants from the Old "World. A certain number of weeds 

 in that region have come from the west and south, some with rather rapid strides 

 in recent years owing to increased means of communication, and there are also 

 native American weeds, indigenous to the region, which have become strongly 

 aggressive through changed conditions. Professor Claypole, of Ohio, has 

 tried to account for the predominance of Old "World weeds in the Atlantic 

 United States by supposing a greater ' plasticity ' in European than in Ameri- 

 can flora (the plant more easily adapting itself, if the change be not too great 

 or sudden, to its new situation, and taking out a new lease of life as a weed). 

 But Professor Gray regards this view as purely hypothetical. Again, Mr. 

 Henslow thinks that weeds or uitrusive dominant plants generally have a com- 

 mon characteristic to which this dominance may be attributed — viz. , that they 

 are in general self -fertilized plants. The question whether the weeds which 

 Europe has given to North America are more self -fertilizing or less subject to 

 cross fertilization than others is examined by Professor Gray, and he is led to 

 answer that self -fertilization is neither the cause nor a perceptible cause of the 

 prepotency referred to. A similar conclusion is justified by a cursory exami- 

 nation of the indigenous weeds of the Atlantic States, and of the prevalent 

 species in California, which (as might be expected) are mostly indigenous spe- 

 cies or immigrants from South America, though the common weeds of the 

 Old World, especially of Southern Europe, are coming in." 



* Ninth Census of the United States, 1872, p. 341. By "improved" land, in 

 the reports on the census of the United States, is meant " cleared land used for 

 grazing, grass, or tillage, or which is now fallow, connected with or belonging 

 to a farm." — Instructions to Marshals and Assistants, Census of 1870, 



