274 Meyen’s Report for 1839 on Physiological Botany. 
whole plant lives but several leaves die. This fact is certain] 
quite true, but we must explain it otherwise. If only a small 
quantity of a poison in a dissolved state is offered to a plant, 
and this poison is not one of the very strongest, like hydro- 
cyanic acid, it is carried up (like all other dissolved sub- 
stances) with the water through the stem into the leaves, 
where the process of digestion takes place; here, therefore, 
the poison collects and kills, but the whole plant does not die 
from its effects, because the quantity was too small to poison 
the large number of cells with their contained sap. 
The practical part of the work begins, properly speaking, 
at page 80, and this section treats most circumstantially of all 
the different substances which have been recommended for 
manuring the soil, and, indeed, as fully as any agriculturist 
can wish ; hundreds of analyses of the manures accompany 
the doctrines which the author brings forward concerning 
their application. This is clearly not the place to give a spe- 
cial account of what service has been done in this purely prac- 
tical part of the work ; we will only mention here observations 
and theories with which the author makes us acquainted in 
order to explain the action of this or that kind of manure, be- 
cause this is in close connection with the study of the nutri- 
tion of plants. 
It appears, from all observations, that food in the bodies of 
animals is not enriched with, but rather exhausted of matters 
fit for manuring, because the nourishing parts are extracted 
and retained by the animals; if however we see sometimes 
that animal excrements produced from a certain quantity of 
- food, manure more powerfully than the food itself, it is only 
to be explained either by the quantity of mineral substances 
which are mixed with excrement, or we deceive ourselves in 
as much as the dung acts powerfully at first but does not exert 
this action for a long time, while the food manures at first 
feebly but afterwards lastingly. The dung of animals will, 
however, always be the worse, the poorer their food is, and in 
proportion as it is better digested and extracted by the ani- 
mal. In speaking of the animal manures, the author al- 
ways draws attention to the development of carbonate of am- 
monia, which is a substance so exceedingly nutritive for plants, 
and states that in the treatment of the dung the principal 
object to be held in view is to retain that ammonia, which may 
be done by solution in water, or still better by combining it — 
with humic acid, which is contained in sufficient quantity in 
mould. With regard to the celebrated manuring with bones 
which has been tried with such great success in England, 
the author says he has convinced himself that nothing but 
