266 APPENDIX TO PART I. 



**And this has been shown by the experiments of Ma- 

 gendie upon dogs, which were fed on sugar, starch, gum, 

 and other substances destitute of nitrogen, and in a very 

 short time pined away and died." 



Difference between different Plants in their power of decom- 

 posing Ammonia; from Daubeny^s Lectures, 



(See Chapter V.) 



**It maybe inferred, from some experiments made by 

 Boussingault, that a great difference exists between plants 

 in their power of assimilating nitrogen, and to this differ- 

 ence that chemist is disposed to attribute the advantage of 

 alternately growing what are called fallow crops, for the 

 purpose of refreshing the soil. 



*'' During germination,' he remarks, *the quantity of 

 azote which seeds contain appears to be on the increase, 

 but there is this curious difference between different kinds, 

 that whilst those of leguminous plants, sown in pure earth 

 and moistened with nothing but distilled water, obtained an 

 increase of nitrogen which the atmosphere alone could 

 have afforded, those of barlev and other cerealia remained 

 in that respect stationary, unless manure were afforded.' 



*' Boussingault also shows in a subsequent memoir, that 

 peas, clover, and other legumes absorb azote, even when 

 planted in a soil that contains no decomposing animal or 

 vegetable matter, but that the cerealia, although if so 

 placed, they may grow, do not appear to secrete this 

 principle. 



*' Boussingault, however, does not go so far as to main- 

 tain, that the latter in no stage of their existence are capa- 

 ble of discharging this function, but only that the plant 

 must have already arrived at a higher state of vigor, in 

 order to derive its supply from such a source. 



"It is on the same principle, that although the animal 

 in general obtains its food from the various organic bodies 

 on which he subsists, yet that in an early stage of existence, 

 before his organs are fitted for undergoing the labor of 

 assimilating such materials, nature has provided him in his 

 mother's milk with aliment already almost elaborated. 



''It is thus, too, that in the seed the embryo is sur- 

 rounded with a mass of albumen, from which it derives its 

 support, until its roots become sufficiently vigorous to 

 extract nourishment from the ground. 



"Hence it becomes in most cases necessary, that crops 



