Agricultural Chemistry — Turnips. 



539 



of such subjects will lead us to deal, and that they very closely 

 represent the exact facts. 



The following dry-matter results refer only to the produce of 

 the third year's experiments (season 1845). The entire series is 

 tabulated. 



Were we to consider each of these results seriatim, with a view 

 to trace the variations in the produce to variations in the compo- 

 sition of the mineral or of the organic manures, we should find nu- 

 merous exceptions to any generahzation to w^hich we might thus 

 be led. When we look, however, at extreme instances, or at 

 series strictly comparable one with another^ we cannot fail to 

 see some undoubted general connexion between the amount 

 of dry matter on the one hand, and such character or stage 

 of growth as we have already observed to result from certain con- 

 ditions of manuring on the other. We must be careful, however, 

 to bear in mind the nature of the substances on which we have 

 been operating, and the various circumstances which have 

 been pointed out as tending to vitiate the legitimacy of any 

 comparisons ; otherwise we may place undue reliance on single 

 results, or, finding these discrepant with others, come to the con- 

 clusion that we have no lesson taught us by so extensive and 

 laborious a course of experiments. With our present limited 

 knowledge, it is, moreover, desirable to exercise great caution in 

 applying to practice the indications of results of this kind. 



It must be remembered, then, that the turnip plant cultivated 

 as food for stock is gathered at no well-defined stage of its growth, 

 but whilst containing a vast amount of circulating fluid, the pro- 

 portion and concentration of which is subject to constant variation 

 under the influence of the still active vital processes of the plant, 

 the varying stores of moisture and of food presented to the roots, and 

 the circumstances of temperature, light, and moisture of the at- 

 mosphere, to which the leaves are exposed. In fact, we might 

 liken the growing turnip to an animal whose gross composition 

 w^ould vary according to his resources of food and drink, and the 

 condition of exhaustion or waste to which he is exposed. At one 

 time his stomach and blood-vessels are full, and at another their 

 contents bear a much lessened relation to the more fixed portion 

 of the body. 



The water existing in the Norfolk white-turnip bulb is seen to 

 constitute more than nine-tenths of its entire weight ; and if it 

 should appear that the proportion varies according to the stage of 

 growth, it will be admitted that the degree of maturity of a suc- 

 culent plant which is to be the subject of a drying experiment^ 

 must be regarded, in deciding its probable yield of solid food, as 

 resulting from various manures ; for if the amount of water is 

 found to decrease accordingly as the plant matures, that one which 



