264 BULLETIN OF THE BUSSEY INSTITUTION. 
Again, 2 hemp seeds planted in 40 grammes of the loam mixed with 
some fragments of quartz (page 309) gave a crop equal to 0.322 
gramme, or five times the seed ; while in a previous year (page 258), 6 
hemp seeds planted in a mixture of 315 grammes quartz sand, 2 
grammes phosphate of lime, and 0.3 gramme ash of hay, gave a crop 
equal to 0.305 gramme, or about twice the weight of the seeds.* 
It is to be remarked that in many of Boussingault’s experiments with 
sand or other inert matters mixed with the ash ingredients of plants, 
but totally devoid of nitrogen, he planted comparatively large seeds, 
such as those of lupins and beans, which contain in themselves so much 
nitrogen that the plants can grow to a considerable height at its ex- 
pense. Attention has already been called in this “ Bulletin,” page 52, to 
the power of such plants to form new shoots and leaves by the repeated 
use of a single measure of nitrogen originally got from the seed. It 
is not at all strange, therefore, that dry crops, weighing three or four 
times as much as the original seed, should sometimes be obtained from 
soils devoid of nitrogen, when the seeds planted are large, and of kinds 
that are rich in nitrogen. 
Doubtless one reason why so severe a conclusion against the signif- 
icance of the soil-nitrogen has been drawn from Boussingault’s experi- 
ments depends upon the indubitable fact that, in cold climates at least, 
there is a very clearly marked and a wide difference between the soil- 
nitrogen and the active forms of that element which are found in 
such compounds as the nitrates and ammonia-salts that are commonly 
used as manures. ‘This difference is to be seen both in respect to the 
rapidity of action of the active forms of nitrogen upon the growth 
of plants, and the comparative slowness of action of the soil-nitrogen, 
and also in the greater or less degree of completeness with which 
the plants can consume the nitrogen of the diverse forms, or, in other 
words, remove it from a given volume of earth. Since one of the 
chief features of Boussingault’s work consisted in the capital illus- 
trations he gave of the great activity and usefulness of the nitrates 
as purveyors of nitrogen to the plant, it is no wonder that he himself 
was disposed to value but lightly the nitrogen of his garden soil when 
he found, for instance (page 321), that a pot containing 0.1 gramme 
of the element in that form gave a crop of hemp weighing only five 
* Compare the early experiment of Boussingault (‘ Agronomie,” 1. 66), in 
which cresses grown in a sufficiency of garden soil yielded abundant crops. 
