Analyses of Ashes of Plants. 



173 



Every means then it is thought should be made use of to pro- 

 duce an early and full development of the leaf of the root crops ; 

 and perhaps no more suitable period in the rotation could be 

 selected by the farmer for the expenditure of the sum which he 

 proposes to invest in artificial manures. This subject will, how- 

 ever, come before us more properly when we have considered the 

 mineral composition of the turnip. 



The next point of attention is the proportion of w^ater in the 

 bulbs and leaves of the turnip. It will be seen, by reference to 

 the table, that the (quantity of water in the bulbs varies between 

 86*0 (Spec. 81) and 92 ' 7 (Spec. 94) per cent. These are the 

 extremes ; the mean of 30 specimens in the table will be found 

 to be 90* 0 per cent. This is rather above than below the number 

 usually assigned to the water of the turnip bulb : but it is on 

 that account the more trustworthy, for it is easier to err in drying 

 these bodies too little than too much.* The water in the leaf 

 has a greater range than in the bulb. The extremes are seen 

 in Spec. 90 and 99, the first of which contains only 70, the second 

 90 per cent. The mean of all the specimens is 85'5. The large 

 leaves appear to contain more water than the smaller ones. It may 

 be thought that the latitude in the proportion of water in the leaves 

 could be accounted for on the supposition that they had become 

 partially and unequally dry before the estimation was commenced. 

 This cannot have been the case, for — although it must not be denied 

 that in the transit of the specimen from a great distance, some small 

 amount of moisture may have passed off, especially from the leaves 

 ■ — it will be seen that the discrepancies occur equally amongst those 

 which were similarly circumstanced in this respect, and that those 

 specimens which were operated on directly they were removed 

 from the soil (those from Mr. Arkell), exhibit an equal extent of 

 difference in the per centage of water. 



The varying quantity of water in turnips is only seen to be a 

 matter of serious import when (as Professor Johnstone has properly 

 observed) it is remembered that upon it very mainly depends the 

 value of the particular specimen in the feeding of stock. It is 

 true that the nutritive properties of any vegetable matter cannot 

 be exactly estimated by the amount of dry w^eight which they 

 represent; one vegetable containing a good deal of indigestible 

 woody matter^ another much easily soluble and digestible sugar 

 and mucilage ; whilst, at the same time, the flesh-forming nitro- 

 genous principles may be in greater or less abundance. But, in 

 ignorance of any differences in this respect in the samples before 

 us, we must estimate the value of each crop by the quantity of 



* For the method of estimating water, see p. 207. We may mention here 

 that they were dried by a prolonged heat of 212= Fahr. 



