THE SOURCES OF THE NITROGEN OF VEGETATION, ETC. 537. 
» The Graminaceous plants of the experiments of 1858 were supplied with a consider-- 
able quantity of combined Nitrogen at an earlier period of growth than those of 1857 
(see Tables showing the dates of addition, Appendix, pp. 542, 543), and they were not 
allowed to exhibit such marked signs of decline of vigour before receiving their fresh- 
supplies. There is, however, no marked distinction in the proportion of the total supply 
appropriated by the plants, and left in the soil, respectively, in the two cases. 
The Graminacee under the title of “1858, A” (those grown in M. G. VILLE’s case) 
were treated similarly to the others of 1858, excepting that the combined Nitrogen was 
given to them at an earlier period of their growth, and they were not allowed to suffer 
at any time for want of it. We shall notice the difference in result presently. 
Jn addition to the evidence of the physiological phenomena as bearing upon the 
amount of growth due to the supply of ammonia, attention should be called to the 
-remarkable character of growth which was manifested. The evidence afforded on this 
head, is of interest in considering the question of the character of the conditions most 
favourable to the assimilation of free Nitrogen; and it also brings to view some remark- 
able features in vegetable physiology. 
It will be seen, by reference to the Notes in the Appendix, that, shortly after the 
addition of ammonia for the first time to the Graminacee (1857 and 1858), the plants 
began to throw out new shoots at the base of the principal stem. It would thus appear 
that the plant, being supplied at the commencement of its growth with only the limited 
quantity of combined Nitrogen contained in its seed, had developed a stem commensu- 
rate with that quantity. But when new quantities of combined Nitrogen were placed 
at the disposal of the plant, forces were thus called into activity which were greater 
than could operate through the medium of the original stem. Some of the new shoots 
have come forth close to the surface of the soil, some at the first, and some at the second 
nodes. The character of growth in this respect can be best studied by reference to the 
drawings of the plants given in Plate XV. 
Another and no less remarkable feature was the formation of roots at the second and 
third nodes above the ground in the case of most of the Graminaceous plants to which 
ammonia-salt was added as manure (see Plate XV.). These roots came out around the 
node, and extended downwards—several of them reaching the soil from heights varying 
from 4 to 13, or even 2 inches, and penetrating it to the bottom of the pot. The most 
marked instance of this kind of growth was that of the barley represented in fig. 11, 
Plate XV., and in more detail, with special reference to the points now under con- 
sideration, in fig. 16, Plate XV. As will be seen in the figures, roots and new stems 
come from the same node, making the latter a veritable starting-point, or new axis 
of growth, like the seed in the first instance. The original stems, below these nodes, 
did not increase much in size beyond what they had attained before the addition of 
ammonia; but the stems above the nodes became much larger than the portions below 
them; as also did those of the new shoots. 
. Finally, so long as the conditions of growth of the plants were such that an addi- 
4D2 
