Dr. Meyen's Researches in Physiological Botany. 137 



quantities of inorganic matters, and the same result was ob- 

 tained on incinerating the chaff, the straw, and the roots ; and 

 it moreover appeared that the roots and chaff were the richest 

 in inorganic substances. The entire plants contained by 

 weight from 3*7 to 4*08 per cent. The quantitative exami- 

 nation of the ashes showed that the quantities of silicic acid, 

 lime, magnesia and alumina were nearly the same in the plants 

 grown on all the different soils. 



The conclusions which M. Lampadius has drawn from these 

 analyses appear certainly quite evident ; but at the same time 

 I may be allowed to remark, that the results would have 

 turned out quite differently if he had chosen some more easily 

 soluble salts as manure, instead of chalk, silicic acid, &c, and 

 that the above experiments would have been much more va- 

 luable if he had before given the analysis of the soil with the 

 manure used ; and therefore I believe that the question as to 

 whether the roots are able to select this or that substance, re- 

 mains completely unanswered by this in other respects highly 

 interesting research. 



M. Boussingault has continued his chemical researches on 

 vegetation*, and has this time chosen as his subject the im- 

 poverishment of the soil and the study of the benefits of " alter- 

 nation (wechselwirthschaft — assolemens f) In the researches 

 of M. Boussingault alluded to in last year's Report, it was 

 shown that plants receive a part of their nourishment from 

 the air; and in the present memoir M. B. endeavours to 

 show that the most fruitful " alternation" (!) is that by which 

 the greatest quantity of elementary bodies is absorbed from 

 the atmosphere. Now it is highly important to know the 

 exact quantities derived from the air, in order to be able to 

 compare the merits of different methods of cultivation. On 

 an estate, with the products of which M. B. was well ac- 

 quainted, it was found, that the manure which was used for 

 one hectare of land contained 2793 kilogrammes carbon. The 

 produce from this piece of land contained on the other hand 

 8383 kilogr. carbon, and from thisM. B. concludes, that the car- 

 bon derived by the plants from the air was at least 5400 kilogr. 

 The given quantity of manure for one hectare of land contained 

 157 kilogr. nitrogen, while the produce contained 251, and 

 therefore the atmosphere must have yielded the excess of 94 



* "De la discussion de la valeur relative des assolemens par l'analyse ele- 



mentaire." — Ann. des Sciences Naturelles, Part. Botan. 1839, t. xi. pp. 31 



—38." 



f Wechselwirthschaft. Different kinds of corn or other plants are culti- 

 vated on a piece of ground in a certain succession for three or more years; the 

 land is then allowed to lie fallow for a certain time, and then the same suc- 

 cession or alternation is proceeded with. 



