62 WAXES GIVEN OFF BY PLANTS DURING THEIR GROWTH. 



probable amount of nitrogen required in the manure of wheat 

 to yield a given amount of it in the increased produce. Since 

 that time we have accumulated much additional evidence on this 

 point, which will enable us to modify or confirm the estimate 

 already hazarded, but which it is not the object or the province 

 of this paper to discuss: the results yet to be obtained, however, 

 in continuation of the inquiry constituting the subject of this 

 report, will, it is anticipated, furnish further data bearing upon 

 this important question. 



Before concluding these observations it seems fitting to call 

 attention to some incidental, yet important indications of these 

 and other of our experiments. Granting, as the conjoint results 

 of the field and of the experimental plants here under discussion 

 would show, that under equal circumstances of growth, and 

 coincidently with the passage into the plant of the same amount 

 of aqueous fluid from the soil, the Leguminous plants will yield 

 a produce varying but little in gross amount from that of the 

 Grarninacese, but containing a much higher per centage, and, 

 consequently, total quantity of nitrogen ; it would, on the view 

 that the analysis of a crop should indicate the manure required 

 for its growth, at once be decided that, of their organic con- 

 stituents, the Leguminous plants should be liberally supplied 

 with nitrogeji, and the Graminaceae rather with carbon. But is 

 this consistent with common usage or the dictates of experiment ? 

 The low nitrogenized and highly carbonaceous gramineous crop 

 requires for its luxuriant growth a large supply of nitrogen by 

 manure ; but with this it seems practically independent of 

 supplied carbon, whilst the highly nitrogenized leguminous 

 plants are, other things being equal, by no means strikingly 

 benefited by nitrogenous manures. We had, indeed, at one 

 time supposed that clover was greatly dependent on an artificial 

 provision of nitrogen, but this view does not appear to be 

 iavoured by further investigation ; whilst with it, as well as with 

 those leguminous plants valued in agriculture for their seeds, a 

 mineral, and especially an alkaline manure seems to be more 

 prominently indicated. 



Again, judging from the composition of the ash of the turnip, 

 which shows both in the leaf and in the bulb a proportion of 

 alkalies to phosphoric acid of 4 or 5 to 1, we should be led to 

 decide that the former rather than the latter were usually and 

 specially the more appropriate manure for the turnip. Common 

 practice has, however, definitely determined in favour of phos- 

 phoric aid rather than on the alkalies. 



Indeed the whole tendency of agricultural investigation seems 

 to show the fallacy of alone relying upon the knowledge of the 

 composition of a crop as directing to the constituents probably 



