Agricultural Chemistri/ — Turnips. 



501 



hand, shows in 1845 the smallest number of rainy days, as well as 

 actual fall of rain, and a mean temperature not so low as in 

 1843. 



In these facts, even though so general and limited in their 

 indications, there is scarcely one which does not show that the 

 most favourable conditions of growth for our cultivated, bulb- 

 forming turnips are, relatively to those for the seed- producing 

 gramineous plants, a low degree of temperature, a large number 

 of rainy days, and a large actual amount of rain. The seeming 

 deviation from this general postulate, which is indicated by the 

 character of the month of October in the third or best turnip 

 season, is, however, by no means inconsistent with our estimate 

 of the requisites of such a season, but rather conduces still further 

 to account for the observed superiority of effect ; for whilst, com- 

 pared with plants which are cultivated for highly elaborated 

 products, such as the cereal grains, we should expect the mainly 

 accumulative and deficiently elaborative processes of the bulb 

 and leaf forming turnip would require a lower degree of tem- 

 perature and a greater amount of moisture favouring the circu- 

 latory determinations of the plants, there is, nevertheless, a point 

 at which depreciation in temperature is injurious to vegetation. 

 Indeed the full growth of the turnip crop depends greatly on the 

 postponement of the winter temperature, and hence probably 

 arose a real advantage from the relatively high (though actually 

 low) temperature in the October of 1845. Again, the lower the 

 temperature, the less important is a continuity and large amount 

 of rain. 



As a general fact, it is evident that the amount of the produce 

 of the turnip is very materially dependent upon the climatic 

 character of the season, not only as in itself a resource, but as an 

 essential agent in the appropriative power of the plant, however 

 liberal and complete may be the supply of constituents within 

 the soil. Whilst, however, it may frequently happen that the 

 physical characters of the season may be such as not to render 

 available to the plant, and at once profitable to the farmer, the 

 constituents which he has provided by manure, it is evident from 

 the results which have been given, that, loithout an ample 

 manuring, the best adapted season is incapable of yielding an 

 agricultural amount of turnips. It is to be feared, however, that 

 it is more frequently the essential condition of artificial aid, 

 rather than that of natural climatic agency and resource, that is 

 in defect. 



Common usage seems to attribute to the turnip and green 

 crops generally a power of collection from the atmosphere which 

 is not recognised in our grain-yielding plants ; and it may at first 

 sight appear inconsistent with this view, that the growth of the 



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