172 



Analijscs of Ashes of Plants. 



field, *r'iye very nearly a like proportion of bulb to leaf. The 

 same thing occurs in Specimens 92 and 93, grown in the same 

 field ; and again, in Specimens 97 and 98, where the leaf in both 

 is extremely small, but very similar in quantity. Another in- 

 stance may be mentioned : Specimens 84 and 86 are Dale's hybrid 

 and green-top white, autumn planted; they were drilled in August 

 on pea stubble, and are remarkable for the large weight of their 

 tops. 



The similarity of proportion in these cases would lead to the 

 inference that whatever errors may attend results obtained on so 

 small a number of plants, the general relation of bulb to leaf is 

 for many purposes sufficiently indicated by them. With the 

 causes which conduce to the observed deviation we have little to 

 do ; these are no doubt various, the age of the plant, the period 

 of planting, the particular culture and manures employed, and 

 the peculiar habits of growth of different varieties (some of which 

 exhibit a greater tendency to drop their leaves than others), each 

 and all of these circumstances might operate in the production of 

 a greater or less quantity of leaf; the influence of such causes, 

 and the extent to which they may be m.ade subservient to the will 

 of the cultivator, can only be satisfactorily ascertained by com- 

 parative trials on the large scale. It may not, however, be out 

 of place here to urge, upon scientific considerations, the import- 

 ance in the root culture of securing* a g-reat breadth of leaf. 



In the cultivation of the cereals it is rather a desideratum (and 

 will become more so every day) to limit the production of straw, 

 a part of the plant of comparatively little value, but at the same 

 time very exhausting to the soil. In the turnip too, it would 

 appear that the leaf is not so valuable as the root, both from the 

 difficulty of preserving it from decay, and its tendency to produce 

 purging in sheep and cattle. 



But there is this difference between the two cases. The straw 

 of the cereals requires a great quantity of vegetable matter for its 

 formatioil, of w hich the greater part, if not all, comes from the soil. 

 But the turnip, as we before said, is not dependent upon the 

 soil for its organic food ; and the increase of the leaves, instead 

 of robbing the tubers, is a source of greater supplies towards 

 iheir formation. The larger the leaves the greater, 'tis true, 

 must be the amount of mineral matter required for these organs ; 

 but it will be seen presently, that even when the leaves are very 

 large indeed, their dem.and for the rarer mineral constituents of 

 the soil is not excessive ; and were this even so, it would be better 

 to insure a full supply of leaf at a small additional expense in 

 artificial manure, than to forego the benefits to be derived from 

 it in the increase of food for stock, and of organic matter in the 

 soil for the succeeding crop. 



