QUESTION OF THE SOURCES OP THE NITROGEN OP VEGETATION. 
71 
to explain facts hitherto not fully explained. On the other hand, should it not be 
established, and a soil source of the whole of the nitrogen of the Leguminosse be 
conclusively proved, the facts of agricultural production would, it seems to us, be 
equally well explained. To this point we shall refer again in our general concluding 
observations. 
7. The Experiments of Professor Emil von Wolff. 
It was also at the Berlin meeting in 1886, at which one of ourselves was present, 
that Professor VON Wolff distributed a page of tabulated results of vegetation 
experiments, made at Hohenheim, and gave some account of them. A preliminary 
series had been made in 1883, and more careful series were conducted in 1884, 1885, 
and 1886. Three sets of experiments. A., B., and C., were made, as follows:— 
A. In wooden boxes, 14’5 cm. (= 5'7 inches) diameter, and 28 cm. (= ll'O inches) 
deep. Into each was put 8 kilog. (= 17'6 lbs.) of calcareous coarse-grained river- 
sand, from which the finest part had been removed by washing. The experimental 
plants were—oats, sand-peas, field-beans, and red clover; and each of these was 
grown under the following conditions ;— 
1. —Without manure. 
2. —With mineral manure, comprising—-superphosphate, magnesium sulphate, 
calcium carbonate, and potassium bicarbonate. 
3. —With the mineral manure, and potassium nitrate = 0'208 gram nitrogen. 
4. —With the mineral manure, and potassium nitrate ~ 0’832 gram nitrogen, 
B. In sheet zinc vessels, 25 cm. (= 9'8 inches) diameter, and 35 cm. (= i3'8 inches) 
deep; into each of which was put 24 kilog. (= 52’9 lbs.) of the washed river-sand. 
These experiments were only made in 1885 and 1886. The plants were oats, and 
sand-peas ; and the same four conditions as to manuring, as above described, were 
adopted; but the quantities used were larger, the amount of nitrogen supplied in 
Experiment 3 being 0'416 gram, and Experiment 4—1'664 gram. 
C. In cement vessels, 50 cm. [= 19'7 inches) diameter and 60 cm. (= 23*6 inches) 
deep. Into each was put 210 kilog. (= 463 lbs.), of the raw unwashed river-sand. 
The conditions of manuring were in kind the same as in A. and B. ; but the 
quantities of nitrogen supplied were, in Experiment 3—0’832 gram, and in Experi¬ 
ment 4—3'328 grams. These experiments were made in 1884, 1885, and 1886 ; and 
the plants were—oats, field-beans, clover, and potatoes. 
At the Berlin meeting in 1886, Professor von Wolff gave only the amounts of 
air-dried above-ground produce; but he has since published, in conjunction with 
Dr. C. Kreuzhage, a long paper, giving a great deal of analytical detail.* It is 
there explained that, for the experiments in wooden boxes (A.), and in zinc vessels 
(B.), fresh washed river-sand was put in each year; but that, for those in the 
cement vessels (C.), the unwashed river-sand first put in was not renewed. 
* “ VegetationsversucEe in Sandkultnr iiber das Verhalten verscEiedener Pflanzen gegen die ZufuEr 
von Salpeterstickstoff.” ‘ LandwirtEscEaftlicEe JaErbucEer,’ vol. 16, Heft 4, 1887, pp. 659 et seq. 
