146 
Lawes and Gilbert have thought to find an explanation of the 
ameliorating influence of leouminous plants on the soil in the fact 
that plants of that kind generally have very long roots and are there- 
fore able to go much deeper in search of their nourishment than the 
depth at w hich the roots of the Graminex are developed; the enrich- 
ing of the earth would therefore be due to the organic débris that culti- 
vation leaves there after the harvest, the nitrogen in which had been 
taken from the subsoil. The defect of this view is that the fertility 
of the soil decreases rapidly as the depth increases, and in the 
majority of cases the subsoil contains only such very insignificant 
quantities of nitrogen that it is impossible to conceive that any plant 
could be nourished by it, particularly a leguminous plant which con- 
tains in its tissues five or six times more nitrogen than does a 
Graminee. 
In a word, the most simple observations of practical agriculture 
show us that the amount of nitrogenous substances furnished by 
nature would not suffice for the requirements of vegetation; it 1s 
therefore indispensable that gaseous nitrogen should interpose di- 
rectly, and that, too, to an important extent, at least for the cultiva- 
tion of leguminous plants. : 
Mr. G. Ville proved this experimentally as early as 1849, and he 
has not ceased repeating it since then, in spite of ae systematic 
opposition of most physiologists and agronomists. 
The primitive experiment of Mr. G. Ville has now become, by 
recent labors in connection with it, an established fact. Allow me, 
then, to describe it briefly, dwelling principally upon its results. 
In a sterile soil, containing at least 1 kilogram of calcined sand, 
various leguminous plants, such as peas, beans, lupins, and others, 
were sown; then were added some nutritive substances, either mineral 
substances alone or a mixture of mineral fertilizers with a small 
quantity of nitrate of soda, the object of which was to aid the young 
plant to pass safely over the critical period of its growth, or, in 
other words, the time when, having exhausted the alimentary re- 
serves provided for it by its cotyledons, it must henceforth nourish 
itself with substances entirely inorganic. 
The plants were watered with pure water free from ammonia; 
every precaution was taken to assure the aeration of the soil; finally 
the plants were kept in as pure an atmosphere as possible; either in 
a glass cage, where from time to time carbonic-acid gas was intro- 
duced, or, what is preferable in the open air, far from the laboratory, 
and, in general, far from everything which could contribute to the 
disengagement of ammonia. 
Under these conditions, and particularly when the soil received no 
nitrogenous fertilizer, the plant remained puny at first, suffering from 
what the German physiologists have called “nitrogen famine.” Some 
plants even do not survive this painful stage of their existence, 
but die without having sensibly increased their dry weight; others, 
nore vigorous, yield a mediocre crop; finally some, by the side of 
other dying stalks, become suddenly very flourishing. Upon the first 
stalk, which up to that time has been lank and without strength, a 
new stalk seems in some way to graft itself—stronger, stiff, turges- 
ce vhich soon becomes covered with broad, well-developed leaves 
of a green that are entirely different from the yellowish tint of the 
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