64 
SIR J. B. LAWBS AND PROFESSOR J. H. GILBERT ON THE 
Indeed, with Dr. Frank, as with other investigators of this subject, a prevailing 
idea seems to be, that there must exist a source of compensation for the loss of 
combined nitrogen by the removal of crops, by drainage, and above all by the 
evolution of free nitrogen from the soil, and in other ways. We believe, however, 
that the losses by the removal of crops are much exaggerated, due account not being 
taken of the return by the manures of the farm ; also that the loss by the evolution 
of free nitrogen by the soil is exaggerated, the results obtained in the laboratory not 
being comparable with the conditions in the field. At tlie same time we believe, 
that such losses as do in reality take place in ordinary agriculture, are not fully com¬ 
pensated ; but that arable soils yielding products for sale, and not receiving nitro¬ 
genous manures from without, do gradually reduce in fertility, so far as them nitrogen 
is concerned. 
6. The Ex 2 )eriments of Professor Hellriegel and Dr. Wilfarth. 
At the Berlin meeting of the Naturforscher-Versammlung, held in September, 
1886, in the Section Landivirthscliaftliclies Versuchsivesen, Professor H. Hell¬ 
riegel gave a paper entitled, “Welche Stickstoffquellen stehen der Pflanze zu 
Gebote ? ” One of ourselves was presiding at the time, and the communication was 
obviously considered by the numerous agricultural chemists present to be one of 
great interest and importance. We have vainly tried to get the paper in extenso f 
but we have now two accounts of the results, one by Hellriegel himself, in the 
‘ Zeitschrift des Vereins fiir die litdienzucker-Industrie des Deutschen Reiches,’ and 
another in a very comprehensive summary of the evidence relating to the sources of 
the nitrogen of vegetation, published by Professor KoNiG.f 
Hellriegel first gave results of experiments with barley, oats, and peas, made in 
pure washed sand, in pots 20 cm. deep, each containing 4 kilograms of the material. 
Nutritive solutions containing no nitrogen were added to all. One series of pots 
received besides, a fixed quantity of nitrogen as nitrate of soda, a second twice as 
much, and a third four times as much. The results showed that in the case of the 
gramineous plants the amount of produce grown had a direct relation to the quantity 
of nitric nitrogen supplied. It was very different with the peas. 
In many comparative experiments he got astonishing growth with peas in the sand 
with all other food substances, but without nitrogen, whilst under exactly similar 
conditions the Graminese showed nitrogen-hunger and failed. He gives the following 
results with peas ;— 
* Ill an interview with Professor Hellriegel, at the meeting of the Naturforscher-Versammlung, 
held at Cologne in September, 1888, we learnt that the details of his experiments have not yet been 
published, but that a full paper is in course of preparation. [October, 1888.] 
‘ Wie kann der Landwirt den Stickstoff-Vorrat in seiner Wirtschafb erhalten nnd vcrmehren ? ’ 
Berlin, 1887. 
