280 BULLETIN OF THE BUSSEY INSTITUTION. . 
be desired. It shows, like the pot experiments previously described, — 
how serviceable the soil-nitrogen may be under favorable conditions ;- 
and, like the experiments in question, it indicates very clearly one at 
least of the conditions that may justly be called favorable. 
It is not improbable, moreover, that in some cases, and perhaps in 
many, certain organic nitrogenous constituents of the soil are con- 
sumed directly by the plant. Since it has been clearly made out that 
plants can take up and feed upon such compounds as urea, uric acid, 
glycocoll, and guanine, there is little reason to doubt that they could 
be equally well nourished by analogous compounds that might be 
formed in the earth. It appears indeed from the experiments of W. 
Wolf,* that plants grown by way of water culture in solutions con- 
taining tyrosin and leucine, substances that are known to be formed 
during the decay of the nitrogenous parts of fresh vegetable and ani- 
mal matter, can obtain a supply of nitrogen from these substances, or 
from some product or products of their decomposition that contain 
neither ammonia nor nitric acid. | 
It is well known that a minute proportion of nitrogenized organic 
matter is to be found in most natural waters, and that traces of such 
matter may be dissolved on thoroughly leaching almost any kind of loam. 
Too little attention has sometimes been paid to the fact that crenic and 
apocrenic acids are nitrogenized bodies.f— According to Mulder, these 
soluble acids occur in not inconsiderable quantities in every fertile 
soil. 
The action of alkaline substances upon vegetable mould has an im- 
portant bearing upon this side of the question. It is not at all improb- 
able that the advantages gained by the use of alkalies as manures and 
in the compost heap may depend in good part directly upon the forma- 
tion of compounds of the alkalies and nitrogenous matters that can 
be used as food by plants. There is no doubt but that, as a general 
rule, the use of the soil-nitrogen by crops is increased by applications of 
wood-ashes and of lime; and, as is well known, the inert nitrogen of 
peat and sods may be made, comparatively speaking, active and assimil- 
able by composting these substances with ‘an alkali, — either ashes, or 
lime, or soda-ash, or a mixture of lime and salt, or even with marl 
* “Die landwirthschaftlichen Versuchs-Stationen,” 1868, 10. 13. 
t Sce Mulder in his ‘‘ Chemie der Ackerkrume,” 1. 349. Compare Detmer, 
“Die landwirthschaftlichen Versuchs-Stationen,” 1871, 14. 270. 
