QTTESTION OF THE SOURCES OF TJIE UITROGPJN OF VEGETATIOX. 
the plants bad gained nitrogen. It is to be observed, however, tljat the results in 
question were those of Boussingault’s earliest experiments, made in 18^^7 and 1838, 
whilst his later results with Leo-uminosae obtained under similar conditions, either 
show slight loss or scarcely appreciable gain. Wolff also quotes experiments of his 
own with clover, made in 1853, in one case in good soil, and in another in the same 
soil previously ignited, when the dry substance of 4 cuttings was, from the natural 
soil 3‘396 grams, but from the ignited soil 20'314 grams; these quantities being 
exclusive of stubble and roots. 
Beferring to his more recent experiments, considerable detail is given as to the 
preliminary series made in 1883, as well as to the more complete series conducted in 
1884, 1885, and 1886, the general conditions of which have been described above, and 
we now confine attention to some further account of the results obtained in the later 
years. 
Wolff states that the washing of the river-sand removed 1‘46 per cent, of it, 
which consisted of sandy clayey matter. He gives a complete mineral analysis of 
both the crude sand, and the separated fine matter. He states that the washed sand 
contained only traces of nitroiren. The separated fine matter contained, however, 
according to a direct determination, 0‘304 per cent, of nitrogen, vdilch seemed to 
exist in humus compounds. It may be observed, that it was, therefore, about twice 
as rich in nitrogen as most ordinary arable surface soils. The results obtained in the 
first year 1884, in the cement vessels, with the unwashed river-sand, show the 
influence of this supply ; but it was concluded that in 1885, and 1886, but little 
remained in a condition available to the plants. 
All the experiments were equally exposed to the influences of air and light, 
excepting that the wooden boxes were placed on a low truck, which was pushed 
under shelter when there was violent or continued rain. All the plants were watered 
with distilled water when there was not sufficient rain ; and in ali cases the drainao-e 
was collected and used for re-watering. The sowing of the seeds was always at the 
end of April; the gathering of the oats, beans, and lupins, at the end of July ; and 
the last cuttings of the clover in August and September. 
To the amounts of above-ground produce (air dried), Wolff now adds the quantity 
of roots, and the total weight including them. He also gives, for the produce of 
1886, the amounts of dry matter, and both the percentages of nitrogen in the dry 
matter, and the actual quantities of nitrogen in the crops, in the case of the “ C ” 
series of experiments, that is, those made in the cement vessels, with the unwashed 
river-sand. In the case of the sand-peas, however, the results of the “ B ” series, that 
is, those made in zinc vessels, with the washed river-sand, are given. The following 
is a summary of the results, so far as the nitrogen is concerned:— 
:HDCCCLXXXIX.—E. 
L 
