Development of Boots of Afjricultural Plants. 
435 
other substances, except potash. As regards nitrogen, Anderson 
is himself doubtful whether it has been correctly estimated. 
Ahrend has examined the oat-plant in a similar way, but 
c?:tended his investigations to the ripening of the seed, and 
exclusive of the roots. It appears that the increase of potash was 
rapid during the time of flowering up to the formation of the 
seed, during the ripening of which there was no further increase ; 
that the increase of phosphoric acid and nitrogen was still more 
rapid during the same period, but that there was an accession of 
phosphoric acid during ripening, and a still greater accession of 
nitrogen. The activity of the leaves, as in the former case, 
during the earlier stages, appears to have been directed towards 
the production of organisable matter to be stored up for the 
shooting stage, and ultimately, as in the turnip, to be employed 
in the formation of seed. The absorptive power of the roots in 
all probability still remains the same, except so far as the increase 
of temperature might stimulate it. The matter, however, at 
present has been very insufficiently studied, and requires further 
and more varied investigation. 
The following are the conclusions which we may gather from 
the preceding remarks : — 
1. That the first effort of vegetation in the sprouting embryo 
is to develope properly the plumule, on which every succeeding 
stage depends. 
That in order to this there must be a proper quantity of nutri- 
ment stored up in the seed, as well as a supply at once available 
from the soil, and that to accomplish this profitably a proper 
selection of seed is highly requisite. 
2. That the second object is to cause such a development of 
the roots as may present a sufficiently large absorbing surface to 
produce a rapid and healthy growth of the vegetative parts of 
the plants ; an end which must be formed by a proper texture 
of the soil, and the presence in it of such chemical constituents 
in their due proportions as are appropriate to the especial crop, 
under cultivation. 
That for this end roots have a certain power of selection, 
rejecting what is injurious, and absorbing in their proper pro- 
portions those elements which the particular nature of the plant 
requires. 
That meanwhile they have no power of excretion, and there- 
fore pauperise the soil merely by comsumption. 
3. Finally, that in many cases certain portions of the roots 
are differentiated as storehouses of nutriment for the fructifying 
stage, while in others the whole mass of roots serves to this 
purpose. 
