THE SOURCES OF THE NITROGEN OF VEGETATION, ETC. 539 
that we failed to get any growth with clover without the addition of ammonia. 
Hence, excepting so far as this fact is itself a point for remark, no contrast can be 
drawn between the growth of this plant with and without an extraneous supply of 
combined Nitrogen. 
From what has already been said, it will be easily understood that the contrast be- 
tween the beans and peas grown with and without the addition of ammonia is not 
very satisfactory. These plants proved to be so sensitive, under the conditions provided 
in the experiments, that it was obvious that, in many cases, they suffered from other 
causes than a want of combined Nitrogen, which we were not able to control. In but 
one experiment with such plants, that with the bean “1858, A.” (Table XIV.), was the 
influence of a supply of combined Nitrogen so marked as to indicate that the plants 
were previously suffering for want of such supply. It will be seen, by reference to the 
Table, that, in the case here referred to, the seeds sown contained 0°0523 gramme of 
Nitrogen, and that 00188 gramme was added in the form of ammonia-salt—making in 
all 0:0711 gramme of combined Nitrogen involved in the experiment. Of this the 
plants appropriated 0:0401 gramme—about one-fifth less, therefore, than was supplied 
in the seeds alone. Yet, although the numerical results, taken by themselves, thus 
afford but little evidence of the effect of the 0:0188 gramme of Nitrogen added in 
the form of ammonia, the increased vigour of growth on the addition did afford such 
evidence. In contrast with this single result, however, attention may be called to the 
results with the beans grown without any other supply of combined Nitrogen than that 
contained in the seed sown. The bean plants so grown in 1857, appropriated nearly 
four-fifths of the Nitrogen of their seed; and those grown in a similar way in 1858, 
appropriated a considerably larger proportion of the combined Nitrogen so provided 
to them. 
From a review of the whole of the results considered in this Section, it appears, then, 
that in the case of the Graminaceous plants experimented upon the growth was the 
most healthy, and such as provided a wide range of conditions for the assimilation of 
free Nitrogen, provided this were at all possible. The growth of the Leguminous plants 
was not so healthy, and did not, therefore, provide such a wide range of conditions for 
the possible assimilation of free Nitrogen. Nor was the growth of other plants so satis- 
factory as that of the Graminaceous ones. In all, the growth was more or less increased 
by the supply of combined Nitrogen beyond that contained in the seed. The effect of 
such supply was the most marked with the Graminaceous plants—the increase in the 
produce of dry vegetable substance due to extraneous supply of combined ‘Nitrogen 
being, in their case, eight, twelve, and even nearly thirty-fold, according to the amount 
of Nitrogen so provided. Yet, with nineteen experiments with Graminaceous plants, 
six with Leguminous ones, and some with plants of other descriptions—with such great 
variation in the amount and character of growth in the several cases—and with such 
great variation in the amount of combined Nitrogen involved in the experiments, in 
