534 



Agricultural Chemistry — Turnips. 



sucli as are more fusiform, and betray a more abundarit seed- 

 forming habit — in this case it is not the most abundant natural 

 seed that is the object of culture, but a seed having a special 

 habit of growth, which habit it is wished to propagate. 



There being an evident understood subserviency of the leaf of 

 the turnip to the bulb, and a sort of succession in the order of 

 maturation of these different organs, the latter not being perfected 

 until the former has lost much of its succulence and vigour ; this 

 fact, and the special conformation of the plant, as before adverted 

 to, have, in theory, led to an appreciation of forcing a large 

 amount of leaf, which is not consistent either with the full 

 efficiency of the conditions which our researches show to favour 

 hulh formation, with the character of the soils best suited to the 

 growth of the turnip-bulb, or that of the plant which is most 

 approved by the practical agriculturist. It is true that rela- 

 tively to wheat and many other plants, the turnip exhibits a large 

 surface of succulent leaf, which, it is admitted, indicates a greater 

 reliance in one way or other upon the atmosphere ; yet all expe- 

 rience, when judging not between the turnip and other plants, 

 but between one turnip and another turnip, values the one in 

 which the proportion of leaf is least and the tendency to bulb the 

 greatest. The description of soil which is called a turnip-soil, 

 again, is just that which is best adapted to formation of fibrous 

 root, and that which always yields a proportionally small amount 

 of leaf. Moreover the soils which yield the largest amount of 

 leaf are known not only by their general mechanical condition, 

 but by their comparative richness in nitrogen, to be exactly those 

 in which the results of our experiments would lead us to anticipate 

 that the leaf-forming tendency would predominate. In these too, 

 as compared with the lighter ones, an excess of nitrogen in the 

 manure is the more likely to give an undesirable development, for 

 in the latter any increased vigour of growth arising from nitro- 

 genous agency may more easily extend the underground organs 

 and determine to bulb-formation than in the former. 



We have now given a history of our experiments upon turnip 

 culture during the first three seasons of their course, so far as the 

 conduct of them in the field is concerned, though none, as yet, 

 of the results obtained in the two succeeding seasons, the last of 

 which is now drawing to a close. Details of this kind having, 

 however, already taken up much space, and sufficed, we hope, to 

 elucidate some established rules of practice, we shall defer until 

 a future occasion a further consideration of this branch of our 

 evidence, and enter at once into an account of our researches in 

 the laboratory, as tending not only to confirm or confute con- 



