mbers in the subjoined table:--

Wood 1
Seeds 3
Stems and straws 5
Roots and tubers 7
Bark 7
Leaves 13

The differences in the quantity of ash contained in different parts of
plants are obviously intended to serve a useful purpose, and it is
interesting to observe that the wood which is destined to remain for a
long period, sometimes for several centuries, a part of the plant,
contains the smallest proportion, and it is not improbable that what it
does contain is really due, not to the actual woody matter itself, but
to the sap which permeates its vessels. By this arrangement but a small
proportion of these important mineral matters, which the soil supplies
in very limited quantity, is locked up within the plant, and those which
are absorbed, after circulating through it, and fulfilling their
allotted functions, are accumulated in the leaves, and annually returned
to the soil.

The different proportions of mineral matters contained in the individual
organs of plants is most strikingly illustrated when parallel
experiments are made on the same species; but the number of instances in
which a sufficiently extensive series of analyses has been made to show
this, is comparatively limited, and is confined to the oat, the
orange-tree, and the horse chesnut--each of which has formed the subject
of a very elaborate investigation. The following table gives the results
obtained on the oat:--

+-------------+-----------+---------+-----------+-------+-------+------+
| | Hopetoun | Hopetoun| Potato | Black | Sandy | |
| | Oats, | Oats, | Oats, | Oats, | Oats, | Mean.|
| | North- | Fife- | North- | Edin- | Fife- | |
| | umberland.| shire. | umberland.| burgh.| shire.| |
+-------------+-----------+---------+-----------+-------+-------+------+
| Grain | 2.14 | 1.81 | 2.22 | 2.11 | 1.76 | 2.00|
| Husk | 6.47 | 6.03 | 6.99 | 8.24 | 6.03 | 6.75|
| Chaff | 16.53 | 17.23 | 15.59 | 19.19 | 18.97 | 16.06|
| Leaves | 8.44 | 7.19 | 14.59 | 10.29 | 15.92 | 10.88|
| Upper part | | | | | | |
| of straw | 4.95 | 5.44 | 9.22 | 8.25 | 11.0 | 7.77|
| Middle part | | | | | | |
| of straw | 6.11 | 5.23 |