300 
Nutrition of Vegetables. 
Having* thus examined these plants, I thought it might not be 
amiss to compare their produce with that of some others, which 
had grown in common garden mould. Of these dried 372 gr. af- 
forded but 34 of ashes, which it is true were very saline, and 
yielded 16 gr. of saline matter, consisting of carbonate and sul- 
phate of potash. In the incineration of these plants too T observ- 
ed a very copious production of ammonia, on pouring a little wa- 
ter on their ashes while still hot. 
But whence come these earths, alkalies, acids, metals, sulphur, 
phosphorus, found in plants, that have had no aliment but pure 
water? Can vitality, in conjunction with light and heat, deter- 
mine certain quantities of oxygen and hydrogen to form by pe- 
culiar condensations those substances which have been consider- 
ed as simple ? this might put us on examining in a new point of 
view all those substances, that chemistry has not yet been able 
to decompose, and thus perhaps the conjectures, that have been 
advanced by some, may be verified. 
We may even extend these remarks to animalization, support- 1 
ed by the well known experiment of Rondeletius, who kept a 
fish in pure water, till it grew too large for the vessel contain- 
ing it, and by other similar experiments on different animals. It 
would even seem, that food acts on the stomach in a great mea- 
sure as mould does on the roots of plants, merely retaining water i 
in such a state of division, as to fit it for absorption and assimila- 
tion. 
From what has been said it appears, that foreign matters dis- 
solved in water only check the progress of vegetation ; but that 
the vital powers can sometimes surmount these obstacles, appro- 
priating only the pure water, that held these matters in solution. 
If experiments founded on long practice were still necessary to 
prove, that the soil is so much the more proper for vegetation in 
proportion as it is deprived of soluble foreign matter, I would 
mention the practice of paring and burning wastes, used chiefly 
in England. Lands thus treated remain in heart a long time ; 
the parts where the heaps of surface mould were burned are 
most fertile; and manure even appears to be injurious, by caus- 
ing the wheat to run chiefly to straw, with thin ears, and those of 
bad quality. 
This extraordinary effect of torrefaction on the soil appears to 
me attributable to the combustion of those excrementitious mat- 
ters, which are ejected by the roots of plants. When the soil is 
