60 THE PLANT. 



If we consider, that, in the cited experiment with 

 the French bean, a great part of the additional unazo- 

 tised substances which were produced fell away in the 

 dying leaves from the body of the plant, it will be seen 

 that the supply of mineral substances was of 110 use to 

 the bean-plant in the absence of nitrogenous food. 



Lastly, it is quite intelligible that the amount of 

 azotised matter contained in a bean might perhaps suf- 

 fice to sustain for years the vegetation of one of the 

 conifers with persistent leaves, and to produce many 

 hundred perhaps many thousand times its own 

 weight of woody substance ; and that such a plant 

 upon a barren soil altogether unsuited for other plants, 

 might thrive with a very sparing supply of nitrogenous 

 food, if the soil contained a proper store of those min- 

 eral substances which are indispensable for the genera- 

 tion of unazotised matter. 



The growth of a plant essentially consists in the en- 

 largement and multiplication of the organs of nutrition, 

 i. e. the leaves and roots. The enlargement of the first, 

 or the production of a second leaf or root fibre, requires 

 the same conditions as the production of the first. The 

 analysis of the seeds teaches us with tolerable certainty 

 what these conditions are. In the normal conditions of 

 nutrition, the first roots and leaves, whose elements were 

 supplied by the seed, produce from certain mineral sub- 

 stances organic compounds, which become parts and 

 constituents of themselves, or constituents of fresh leaves 

 and roots, consisting of the same elements and having 

 the identical properties of the first, i. e. they possess the 

 same power to transform inorganic nutritive substances 

 into organic formative materials. 



It is quite clear that the enlargement of the first 

 leaves and roots and the production of new ones, must 

 have required azotised and unazotised substances in the 

 same proportion as in the seed, which makes it probable 

 that the organic operations of the plant under the do- 

 minion of sunlight uniformly produce in all periods of 

 growth the same materials, i. e. the constituent ele- 

 ments of the seed, which serve to build up the plant, 



