THE INORGANIC CONSTITUENTS OF PLANTS.
When treating of the general constituents of plants, it has been already
stated that the older chemists and vegetable physiologists, misled by
the small quantity of ash found in them, entertained the opinion that
mineral matters were purely fortuitous components of vegetables, and
were present merely because they had been dissolved and absorbed along
with the humus, which was then supposed to enter the roots in solution,
and to form the chief food of the plant. This supposition, which could
only be sustained at a time when analysis was imperfect, has been long
since disproved and abandoned, and it has been distinctly shown by
repeated experiment that not only are these inorganic substances
necessary to the plant, but that every one of them, however small its
quantity, must be present if it is to grow luxuriantly and arrive at a
healthy maturity. The experiments of Prince Salm Horstmar, before
alluded to, have established beyond a doubt, that while a seed may
germinate, and even grow, to a certain extent, in absence of one or more
of the constituents of its ash, it remains sickly and stunted, and is
incapable of producing either flower or seed.
Of late years the analysis of the ash of different plants has formed the
subject of a large number of laborious investigations, by which our
knowledge of this subject has been greatly extended. From these it
appears that the quantity of ash contained in each plant or part of a
plant is tolerably uniform, differing only within comparatively narrow
limits, and that there is a special proportion belonging to each
individual organ of the plant. This fact may be best rendered obvious by
the subjoined table, showing the quantity of ash contained in a hundred
parts of the different substances dried at 212 deg.. Most of these numbers
are the mean of several experiments:--
_Table showing the quantity of inorganic matters in 100 parts of
different plants dried at 212 deg.._
SEEDS.
Wheat 1.97
Barley 2.48
Oats (with husk) 3.80
Oats (without husk) 2.06
Rye 2.00
Millet 3.60
Rice 0.37
Maize 1.20
Peas 2.88
Beans 3.22
Kidney Beans 4.09
Lentils 2.51
Tares 2.60
Buckwheat 2.13
Linseed 4.40
Hemp seed 5.60
Rape seed 4.35
Indian Rape-seed[A] 4.06
Sunflower 3.26
Cotton seed 5.93
Guinea Corn 1.99
Gold of Pleasure 4.10
White Mustard 4.15
Black Mustard 4.31
Poppy 6.56
Niger seed (_Guizotia oleifera_) 7.00
Earth nut 3.88
Sweet Almond 4.90
Horse-chesnut 2.81
Grape 2.76
Clover 6.19
Turnip 3.98
Carrot 10.03
Sainfoin 5.27
Italian Ryegrass 6.91
Mangold-Wurzel 6.58
STRAWS AND STEMS.
Wheat 4.54
Barley 4.99
Oat 7.24
Winter Rye 5.15
Summer Rye 5.78
Millet 8.32
Maize 3.60
Pea 4.81
Bean 6.59
Tares 6.00
Lentil 5.38
Buckwheat 4.50
Hops 4.42
Flax straw 4.25
Hemp 4.14
Gold of Pleasure 6.05
Rape 4.41
Potato 14.90
Jerusalem Artichoke 4.40
ENTIRE PLANT.
Potato 17.70
Spurry 10.06
Red Clover 8.79
White Clover 8.72
Yellow Clover 8.56
Crimson Clover (_T. incarnatum_) 10.81
Cow Grass (_T. medium_) 11.31
Sainfoin 6.51
Ryegrass 6.42
Meadow Foxtail (_Alopecurus pratensis_) 7.81
Sweet-scented Vernal Grass (_Anthoxanthum odoratum_) 6.32
Downy Oat Grass (_Avena pubescens_) 5.22
Bromus erectus 5.21
Bromus mollis 5.82
Cynosurus cristatus 6.38
Dactylis glomeratus 5.31
Festuca duriuscula 5.42
Holcus lanatus 6.37
Hordeum pratense 5.67
Lolium perenne 7.54
Poa annua 2.83
Poa pratensis 5.94
Poa trivialis 8.33
Phleum pratense 5.29
Plantago lanceolata 8.68
Poterium Sanguisorba 7.97
Yarrow 13.45
Rape Kale 8.00
Cow Cabbage 10.00
Asparagus 6.40
Parsley 1.10
Furze 3.11
Chamomile (_Anthemis arvensis_) 9.66
Wild Chamomile (_Matricaria Chamomilla_) 9.10
Corn Cockle (_Agrostemma Githago_) 13.20
Corn Blue Bottle (_Centaurea Cyanus_) 7.32
Foxglove 10.89
Hemlock (_Conium maculatum_) 12.80
Sweet Rush (_Acorus Calamus_) 6.90
Common Reed (_Arundo Phragmites_) 1.44
Celandine (_Chelidonium majus_) 6.85
Equisetum fluviatile 23.60
Equisetum hyemale 11.80
" arvense 13.80
" linosum 15.50
Fucus nodosus 19.03
Fucus vesiculosus 27.63
Laminaria digitata 39.68
LEAVES.
Turnip 9.37
Beet 20.30
Kohl-rabi 18.54
Carrot 10.95
Jerusalem Artichoke 28.30
Hemp 22.00
Hop 17.25
Tobacco 22.62
Spinach 19.76
Chicory 15.67
Poplar 23.00
Red Beech 6.00
White Beech 10.51
Oak 9.80
Elm 16.33
Horse-chesnut 9.08
Maple 28.05
Ash 14.76
Fir 2.31
Acacia 18.20
Olive 6.45
Orange 13.73
Potato 15.10
Tussac Grass 7.15
ROOTS AND TUBERS.
Potato 4.16
Jerusalem Artichoke 5.38
Turnip 13.64
Beet 8.27
Kohl-rabi 6.08
Rutabaga 7.34
Carrot 5.80
Belgian White Carrot 6.22
Mangold-Wurzel 8.78
Parsnip 5.52
Radish 7.35
Chicory 5.21
Madder 8.33
WOODS.
Beech 0.38
Apple 1.29
Cherry 0.28
Birch 1.00
Oak 2.50
Walnut 1.57
Lime 5.00
Horse-chesnut 1.05
Olive 0.58
Mahogany 0.81
Vine 2.57
Larch 0.32
Fir 0.14
Scotch Fir 0.17
Filbert 0.50
Chesnut 3.50
Poplar 0.80
Hazel 0.50
Orange 2.74
Vine 2.57
BARKS.
Beech 6.62
Cherry 10.37
Fir 1.79
Oak 6.00
Horse-chesnut 7.85
Filbert 6.20
Cork 1.12
FRUITS.
Plum 0.40
Cherry 0.43
Strawberry 0.41
Pear 0.41
Apple 0.27
Chesnut 0.99
Cucumber 0.63
Vegetable Marrow 5.10
On examining this table it may be observed that, notwithstanding the
very great variety in the proportion of ash in different plants, some
general relations may be traced. A certain similarity may be observed
between those belonging to the same natural family, the seeds of all the
cereal grains, for instance, containing in round numbers two per cent of
inorganic matters. Leguminous seeds (peas and beans) contain about three
per cent, while in rape-seed, linseed, and the other oily seeds, it
reaches four per cent. In the stems and straws less uniformity exists,
but with the exception of a few extreme cases, the quantity of ash in
general approaches pretty closely to five per cent. Still more
diversified results are obtained from the entire plants; but this
diversity is probably much more apparent than real, and must be, in part
at least, dependent on the proportion existing between the stem and
leaves, for the leaves are peculiarly rich in ash, and a leafy plant
must necessarily yield a higher total percentage of ash, although, if
stems and leaves were separately examined, they might not show so
conspicuous a difference.
The leaves surpass all other parts of plants, in the proportion of
inorganic constituents they contain, the table showing that in some
instances, as in the maple and Jerusalem artichoke, they exceed
one-fourth of the whole weight of the dry matter. In other leaves, and
more especially in those of the coniferae, the proportion is much
smaller. Taking the average of all the analyses hitherto made, it
appears that leaves contain about thirteen per cent of ash, but the
variations on either side are so large that little value is to be
attached to it except as an indication of the general abundance of
mineral matters.
In roots and tubers the variations are less, and all, except the potato
and the turnip, contain about seven per cent of ash.
The smallest proportion of mineral matter is found in wood. In one case
only does the proportion reach five per cent, while the average scarcely
exceeds one, and in the fir the quantity amounts to no more than one
six-hundredth of the dry matter. In the bark the quantity is much
larger, and may be stated at seven per cent.
The general proportion of ash found in different parts of plants is
given in round numbers 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 | 7.41 | 6.53 | 9.01 | 6.66|
| Lower part | | | | | | |
| of straw | 5.33 | 5.18 | 9.76 | 7.11 | 7.30 | 6.93|
+-------------+-----------+---------+-----------+-------+-------+------+
The specimens of oats on which these analyses were made were from
different districts of country, grown on soils of different quality, and
were, further, of different varieties; and yet they show, on the whole,
a remarkable similarity in the proportion of ash in each part, and
indicate that there is a normal quantity belonging to it. Such a series
of analyses also affords the most convincing proof that the inorganic
matters cannot be fortuitous, and merely absorbed from the soil along
with their organic food, as the old chemists supposed, because, in that
case, they ought to be uniformly distributed throughout the entire
plant, and not accumulated in particular proportions in each individual
organ.
Not only does the proportion of ash vary in the different parts of a
plant, but even in the same part it is greatly influenced by its period
of growth. The laws which regulate these variations are very imperfectly
known, but in general it is observed that during the period of active
growth the quantity of ash is largest. Thus, it has been found that in
early spring the wood of the young shoots of the horse-chesnut contains
9.9 per cent of ash. In autumn this has diminished to 3.4, and the last
year's twigs contain only 1.1 per cent, while in the old wood the
quantity does not exceed 0.5. Saussure has also observed that the
quantity of ash diminishes in certain plants when the seed has ripened.
Thus, he found that the percentages of ash, before flowering, and after
seeding, were as follows:--
Before flowering. With ripe seed.
Sunflower 14.7 9.3
Wheat 7.9 3.3
Maize 12.2 4.6
On the other hand, the quantity of ash in the leaves of trees increases
considerably in autumn, as shown by this table:--
PER-CENTAGE OF ASH IN
May. September.
Oak leaves 5.3 5.5
Poplar 6.6 9.3
Hazel 6.1 7.0
Horse-chesnut 7.2 8.6
In general, the proportion of ash appears to increase as the plant
reaches maturity, and this is particularly seen in the oat, of which
very complete analyses have been made at different periods of its
growth:--
_Proportion of Ash in different parts of the Oat at different periods of
its growth._
+--------------+---------+---------+--------+------------+
| | | | | Grain |
| Date. | Stalks. | Leaves. | Chaff. | with husk. |
+--------------+---------+---------+--------+------------+
| 2d July | 7.83 | 11.35 | ... | 4.91 |
| 9th July | 7.80 | 12.20 | ... | 4.36 |
| 16th July | 7.94 | 12.61 | 6.00 | 3.38 |
| 23d July | 7.99 | 16.45 | 9.11 | 3.62 |
| 30th July | 7.45 | 16.44 | 12.28 | 4.22 |
| 5th August | 7.63 | 16.05 | 13.75 | 4.31 |
| 13th August | 6.62 | 20.47 | 18.68 | 4.07 |
| 20th August | 6.66 | 21.14 | 21.07 | 3.64 |
| 27th August | 7.71 | 22.13 | 22.46 | 3.51 |
| 3d September | 8.35 | 20.90 | 27.47 | 3.65 |
+--------------+---------+---------+--------+------------+
The increase is here principally confined to the leaves and chaff, while
the stalks, which owe their strength to a considerable extent to the
inorganic matters they contain, are equally supplied at all periods of
their growth. In the grain only is there a diminution, but this is
apparent and not real, and is due to the fact that the determination of
the quantity of ash, as made on the grain with its husk, and the former,
which contains only a small quantity of mineral matters, increases much
more rapidly in weight than the latter, when it approaches the period of
ripening, and it is accordingly during the last three weeks of its
growth that this diminution becomes apparent.
The nature of the soil has also a very important influence on the
proportion of mineral matters, and of this an interesting illustration
is given in the following table, which shows the quantities found in the
grain and straw of the same variety of the pea grown on fourteen
different soils:--
+----+-------+--------+
| | Seed. | Straw. |
+----+-------+--------+
| 1 | 2.30 | |
| 2 | 3.25 | 3.43 |
| 3 | 4.27 | 3.62 |
| 4 | 3.40 | 3.39 |
| 5 | 2.99 | 3.90 |
| 6 | 3.19 | 6.80 |
| 7 | 2.53 | 3.90 |
| 8 | 2.27 | 6.59 |
| 9 | 2.69 | 3.49 |
| 10 | 1.61 | 3.91 |
| 11 | 3.11 | 5.28 |
| 12 | 3.34 | 7.57 |
| 13 | 2.78 | 3.76 |
| 14 | 3.01 | 3.38 |
+----+-------+--------+
Although those differences are very large, especially in the straw, and
must be attributed to the soil, it has hitherto been found impossible to
ascertain the nature of the relation subsisting between it and the crops
it yields; indeed, it must obviously be dependent on very complicated
questions, which cannot at present be solved, for it may be observed
that the increase in the grain does not occur simultaneously with that
in the straw, and in several cases a large proportion of ash in the
former is associated with an unusually small amount in the latter. _A
priori_, it might be expected that those soils which are especially rich
in the more important constituents of the ash should yield a produce
containing more than the average quantity, but this is very far from
being an invariable occurrence, and not unfrequently the very reverse
is the case. In some instances the variations may be traced to the soil,
as in the following analyses of the fruit of the horse-chesnut, grown on
an ordinary forest soil, and on a rich soil, produced by the
disintegration of porphyritic rock, in which the latter yields a much
larger quantity of ash:--
Kernel of seed. Green husk. Brown husk.
Forest soil 2.26 4.53 1.70
Porphyry soil 3.36 7.29 2.20
In the majority of instances we fail to establish any connection between
the nature of the soil and the plants it yields, chiefly because we are
still very deficient in analyses of those grown on uncultivated soils;
and on cultivated land it is impossible to draw conclusions, because the
nature of the manure exerts an influence quite as great, if not greater,
than that of the soil itself.
The relative proportion in which the different mineral matters enter
into the composition of the ash varies within very wide limits, as will
be apparent from the following table, containing a selection of the best
analyses of our common cultivated and a few uncultivated plants.
_Table of the Composition of the Ash of different Plants in 100 Parts._
_Note._--Alumina and oxide of manganese occur so rarely, that separate
columns have not been introduced for them, but their quantity is stated
in notes at the end of the table.
+---------------------+--------+------+-----------+---------+------+----------+
| | Potash.| Soda.| Chloride | Chloride| Lime.| Magnesia.|
| | | | of | of | | |
| | | | Potassium.| Sodium. | | |
+---------------------+--------+------+-----------+---------+------+----------+
|Wheat, grain | 30.02 | 3.82 | ... | ... | 1.15| 13.39 |
| straw | 17.98 | 2.47 | ... | ... | 7.42| 1.94 |
| chaff | 9.14 | 1.79 | ... | ... | 1.88| 1.27 |
|Barley, grain | 21.14 | ... | 5.65 | 1.01 | 1.65| 7.26 |
| straw | 11.22 | ... | ... | 2.14 | 5.79| 2.70 |
|Oats, grain[B] | 20.63 | ... | 1.03 | ... | 10.28| 7.82 |
| straw | 19.46 | 1.93 | 2.71 | 4.27 | 7.01| 3.79 |
| chaff[C] | 6.33 | 3.93 | ... | 0.24 | 1.95| 0.38 |
|Rye, grain | 33.83 | 0.39 | ... | ... | 2.61| 12.81 |
| straw | 17.20 | ... | 0.30 | 0.60 | 9.10| 2.40 |
|Maize, grain | 28.37 | 1.74 | ... | trace | 0.57| 13.60 |
| stalks and leaves | 35.26 | ... | ... | 2.29 | 10.53| 5.52 |
|Rice, grain | 20.21 | 2.49 | ... | ... | 7.18| 4.26 |
|Buckwheat, straw | 31.71 | ... | 7.42 | 4.55 | 15.71| 1.66 |
|Peas (gray), seed | 41.70 | ... | 3.82 | 1.24 | 4.78| 5.78 |
| straw | 21.30 | 4.22 | ... | ... | 37.17| 7.17 |
|Beans (common field),| | | | | | |
| grain | 51.72 | 0.54 | ... | ... | 5.20| 6.90 |
| straw | 32.85 | 2.77 | ... | 11.54 | 19.85| 2.53 |
|Tare, straw | 32.82 | ... | 3.27 | 4.03 | 20.78| 5.31 |
| straw | 31.72 | ... | 7.41 | 4.55 | 15.71| 1.66 |
+---------------------+--------+------+-----------+---------+------+----------+
+-----------------------+-------+------------+-----------+----------+---------+
| | Oxide | Phosphoric | Sulphuric | Carbonic | Silica. |
| | of | Acid. | Acid. | Acid. | |
| | Iron. | | | | |
+-----------------------+-------+------------+-----------+----------+---------+
| Wheat, grain | 0.91 | 46.79 | ... | ... | 3.89 |
| straw | 0.45 | 2.75 | 3.09 | ... | 63.89 |
| chaff | 0.37 | 4.31 | ... | ... | 81.22 |
| Barley, grain | 2.13 | 28.53 | 1.91 | ... | 30.68 |
| straw | 1.36 | 7.20 | 1.09 | ... | 68.50 |
| Oats, grain | 3.85 | 50.44 | ... | ... | 4.40 |
| straw | 1.49 | 5.07 | 3.35 | 1.36 | 49.56 |
| chaff | 1.58 | 1.04 | 9.61 | ... | 72.85 |
| Rye, grain | 1.04 | 39.92 | 0.17 | ... | 9.22 |
| straw | 1.40 | 3.80 | 0.80 | ... | 64.50 |
| Maize, grain | 0.47 | 53.69 | ... | ... | 1.55 |
| stalks and leaves | 2.28 | 8.09 | 5.16 | 2.87 | 27.98 |
| Rice, grain | 2.12 | 62.23 | ... | ... | 1.37 |
| Buckwheat, straw | ... | 10.34 | 4.67 | 20.37 | 3.57 |
| Peas (gray), seed | 0.18 | 36.50 | 4.47 | 0.82 | 0.68 |
| straw | 1.07 | 4.65 | 8.68 | 12.48 | 3.23 |
| Beans (common field), | | | | | |
| grain | ... | 28.72 | 3.05 | 3.42 | 0.42 |
| straw | 0.61 | 0.49 | 1.40 | 25.32 | 2.61 |
| Tare, straw | 0.65 | 10.59 | 2.52 | 18.73 | 1.28 |
| straw | ... | 10.34 | 4.67 | 20.37 | 3.57 |
+-----------------------+-------+------------+-----------+----------+---------+
+---------------------+--------+------+-----------+---------+------+----------+
| | Potash.| Soda.| Chloride | Chloride| Lime.| Magnesia.|
| | | | of | of | | |
| | | | Potassium.| Sodium. | | |
+---------------------+--------+------+-----------+---------+------+----------+
|Flax, seed | 34.17 | 1.69| ... | 0.36 | 8.40| 13.11 |
| straw | 21.53 | 3.68| ... | 9.21 | 21.20| 4.20 |
|Rape, seed[D] | 16.33 | 0.34| ... | 0.96 | 8.30| 8.80 |
| straw[E] | 16.63 | 10.57| ... | 2.53 | 21.51| 2.92 |
|Spurry | 26.12 | 1.14| ... | 8.90 | 14.46| 8.88 |
|Chicory root | 34.64 | ...| 8.92 | 2.98 | ...| ... |
|Red clover | 25.60 | ...| 9.08 | 6.02 | 21.57| 8.47 |
|Cow grass, | | | | | | |
| _Trifolium medium_ | 22.78 | ...| 12.39 | 1.86 | 24.42| 8.86 |
|Yellow clover | 27.48 | ...| 11.72 | 8.16 | 17.26| 8.39 |
|Alsike clover | 29.72 | ...| 6.29 | 1.05 | 26.83| 4.01 |
|Lucerne | 27.56 | ...| 11.64 | 1.91 | 20.60| 5.22 |
|Anthoxanthum odoratum| 32.03 | ...| 7.03 | 4.90 | 9.21| 2.53 |
|Alopecurus pratensis | 37.03 | ...| 9.50 | ... | 3.90| 1.28 |
|Avena pubescens | 31.21 | ...| 4.05 | 5.66 | 4.72| 3.17 |
|Bromus erectus | 20.33 | ...| 10.63 | 1.38 | 10.38| 4.99 |
|Bromus mollis | 30.09 | 0.33| ... | 3.11 | 6.64| 2.60 |
|Cynosurus cristatus | 24.99 | ...| 11.60 | ... | 10.16| 2.43 |
|Dactylis glomerata | 29.52 | ...| 17.86 | 3.09 | 5.82| 2.22 |
|Festuca duriuscula | 31.84 | ...| 8.17 | 0.62 | 10.31| 2.83 |
|Holcus lanatus | 34.83 | ...| 3.91 | 6.66 | 8.31| 3.41 |
|Lolium perenne | 24.67 | ...| 13.80 | 7.25 | 9.64| 2.85 |
|Annual ryegrass | 28.99 | 0.87| ... | 5.11 | 6.82| 2.59 |
|Poa annua | 41.86 | ...| 0.47 | 3.35 | 11.69| 2.44 |
|Poa pratensis | 31.17 | ...| 11.25 | 1.31 | 5.63| 2.71 |
|Poa trivialis | 29.40 | ...| 6.90 | ... | 8.80| 3.22 |
|Phleum pratense | 31.09 | ...| 0.70 | 3.24 | 14.94| 5.30 |
|Plantago lanceolata | 33.26 | ... | 4.53 | 8.80 | 19.01| 3.51 |
|Poterium Sanguisorba | 30.26 | ... | 3.27 | 1.35 | 24.82| 4.21 |
|Achillea Millefolia | 30.37 | ... | 20.49 | 3.63 | 13.40| 3.01 |
|Potato, tuber | 43.18 | 0.09| ... | 7.92 | 1.80| 3.17 |
| stem | 39.53 | 3.95| ... | 20.43 | 14.85| 4.10 |
| leaves | 17.27 | ... | 4.95 | 11.37 | 27.69| 7.78 |
|Jerusalem Artichoke | 55.89 | ... | 4.88 | ... | 3.34| 1.30 |
| stem | 38.40 | 0.69| ... | 4.68 | 20.31| 1.91 |
| leaves | 6.81 | 3.72| ... | 1.82 | 40.15| 1.95 |
|Turnip, seed | 21.91 | 1.23| ... | ... | 17.40| 8.74 |
| bulb | 23.70 | 14.75| ... | 7.05 | 11.82| 3.28 |
| leaves | 11.56 | 12.43| ... | 12.41 | 28.49| 2.62 |
|Mangold Wurzel, root | 21.68 | 3.13| ... | 49.51 | 1.90| 1.79 |
| leaves | 8.34 | 12.21| ... | 37.66 | 8.72| 9.84 |
|Carrot, root | 42.73 | 12.11| ... | ... | 5.64| 2.29 |
| leaves | 17.10 | 4.85| ... | 3.62 | 24.05| 0.89 |
|Kohl-rabi, bulb | 36.27 | 2.84| ... | 11.90 | 10.20| 2.36 |
| leaves | 9.31 | ... | 5.99 | 6.66 | 30.31| 3.62 |
|Cow cabbage, head | 40.86 | 2.43| ... | ... | 15.01| 2.39 |
| stalk | 40.93 | 4.05| ... | 2.08 | 10.61| 3.85 |
|Poppy seed | 9.10 | ... | 7.15 | 1.94 | 35.36| 9.49 |
| leaves | 36.37 | ... | 2.50 | 2.51 | 30.24| 6.47 |
|Mustard seed (white) | 25.78 | 0.33| ... | ... | 19.10| 5.90 |
|Radish root | 21.16 | ... | 1.29 | 7.07 | 8.78| 3.53 |
|Tobacco leaves | 36.37 | ... | 2.50 | 2.51 | 30.24| 6.47 |
|Fucus nodosus[F] | 20.03 | 4.58| ... | 24.33 | 9.60| 6.65 |
|Fucus vesiculosus[G] | 20.75 | 6.09| ... | 24.81 | 8.92| 5.83 |
|Laminaria digitata[H]| 12.16 | ... | 2.30 | 19.34 | 4.62| 10.94 |
+---------------------+--------+------+-----------+---------+------+----------+
+---------------------+-------+------------+-----------+----------+---------+
| | Oxide | Phosphoric | Sulphuric | Carbonic | Silica. |
| | of | Acid. | Acid. | Acid. | |
| | Iron. | | | | |
+---------------------+-------+------------+-----------+----------+---------+
|Flax, seed | 0.50 | 38.54 | 1.56 | 0.22 | 1.45 |
| straw | 5.58 | 7.53 | 3.39 | 15.75 | 7.92 |
|Rape, seed | 1.79 | 31.90 | 5.38 | 5.44 | 19.98 |
| straw | 1.30 | 4.68 | 3.90 | 23.04 | 11.80 |
|Spurry | ... | 10.20 | 1.79 | 27.38 | 1.14 |
|Chicory root | ... | ... | ... | ... | ... |
|Red clover | 1.26 | 4.09 | 2.96 | 18.05 | 1.95 |
|Cow grass, | | | | | |
| _Trifolium medium_ | 1.09 | 4.94 | 2.66 | 20.16 | 1.12|
|Yellow clover | 1.40 | ... | 4.82 | 4.31 | 1.76 |
|Alsike clover | 0.71 | 5.64 | 3.25 | 20.74 | 1.73 |
|Lucerne | 2.23 | 6.47 | 4.80 | 15.94 | 2.63 |
|Anthoxanthum odoratum| 1.18 | 10.09 | 3.39 | 1.26 | 28.35 |
|Alopecurus pratensis | 0.47 | 6.25 | 2.16 | 0.65 | 38.75 |
|Avena pubescens | 0.72 | 10.82 | 3.37 | ... | 36.28 |
|Bromus erectus | 0.26 | 7.53 | 5.46 | 0.55 | 38.48 |
|Bromus mollis | 0.28 | 9.62 | 4.91 | 9.07 | 33.34 |
|Cynosurus cristatus | 0.18 | 7.24 | 3.20 | ... | 40.11 |
|Dactylis glomerata | 0.59 | 8.60 | 3.52 | 2.09 | 26.65 |
|Festuca duriuscula | 0.78 | 12.07 | 3.45 | 1.38 | 28.53 |
|Holcus lanatus | 0.31 | 8.02 | 4.41 | 1.82 | 28.31 |
|Lolium perenne | 0.21 | 8.73 | 5.20 | 0.49 | 27.13 |
|Annual ryegrass | 0.28 | 10.07 | 3.45 | ... | 41.79 |
|Poa annua | 1.57 | 9.11 | 10.18 | 3.29 | 16.03 |
|Poa pratensis | 0.28 | 10.02 | 4.26 | 0.40 | 32.93 |
|Poa trivialis | 0.29 | 9.13 | 4.47 | 0.29 | 37.50 |
|Phleum pratense | 0.27 | 11.29 | 4.86 | 4.02 | 31.09 |
|Plantago lanceolata | 0.90 | 7.08 | 6.11 | 14.40 | 2.37 |
|Poterium Sanguisorba | 0.86 | 7.81 | 4.84 | 21.72 | 0.83 |
|Achillea Millefolia | 0.21 | 7.13 | 2.44 | 9.36 | 9.92 |
|Potato, tuber | 0.44 | 8.61 | 15.24 | 18.29 | 1.94 |
| stem | 1.34 | 6.68 | 6.56 | ... | 2.56 |
| leaves | 4.50 | 13.60 | 6.37 | ... | 6.47 |
|Jerusalem Artichoke | 0.45 | 16.99 | 3.77 | 11.80 | 1.52 |
| stem | 0.88 | 2.97 | 3.23 | 25.40 | 1.51 |
| leaves | 1.14 | 6.61 | 2.21 | 24.31 | 17.25 |
|Turnip, seed | 1.95 | 40.17 | 7.10 | 0.82 | 0.67 |
| bulb | 0.47 | 9.31 | 16.13 | 10.74 | 2.69 |
| leaves | 3.02 | 4.85 | 10.36 | 6.18 | 8.04 |
|Mangold Wurzel, root | 0.52 | 1.65 | 3.14 | 15.23 | 1.40 |
| leaves | 1.46 | 5.89 | 6.54 | 6.92 | 2.35 |
|Carrot, root | 0.51 | 12.31 | 4.26 | 18.00 | 1.11 |
| leaves | 3.43 | 6.21 | 5.08 | 23.15 | 11.61 |
|Kohl-rabi, bulb | 0.38 | 13.45 | 11.43 | 10.24 | 0.83 |
| leaves | 5.50 | 9.43 | 10.63 | 8.97 | 9.57 |
|Cow cabbage, head | 0.77 | 12.53 | 7.27 | 16.68 | 1.66 |
| stalk | 0.41 | 19.57 | 11.11 | 6.33 | 1.04 |
|Poppy seed | 0.41 | 31.38 | 1.92 | ... | 3.24 |
| leaves | 2.14 | 3.28 | 5.09 | ... | 11.40 |
|Mustard seed (white) | 0.39 | 44.97 | 2.19 | ... | 1.31 |
|Radish root | 1.19 | 41.09 | 7.71 | ... | 8.17 |
|Tobacco leaves | 2.18 | 3.24 | 5.09 | ... | 11.40 |
|Fucus nodosus | 0.26 | 1.71 | 21.97 | 6.39 | 0.38 |
|Fucus vesiculosus | 0.35 | 2.14 | 28.01 | 2.20 | 0.67 |
|Laminaria digitata | 0.45 | 1.75 | 7.26 | 15.23 | 1.20 |
+---------------------+-------+------------+-----------+----------+---------+
A simple inspection of this table leads to various interesting
conclusions. It is particularly to be observed that some of the
constituents of the ash are not invariably present, and two at
least--namely, alumina and manganese--are found so rarely as to justify
the inference that they are not indispensable. Of the other substances,
iodine is restricted exclusively to sea-plants, but to them it appears
to be essential. Oxide of iron, which occurs only in small quantities,
has sometimes been considered fortuitous, but it is almost invariably
present, and the experiments of Prince Salm Horstmar leave no doubt that
it is essential to the plant. Its function is unknown, but it is an
important constituent of the blood of herbivorous animals, and may be
present in the plant, less for its own benefit than for that of the
animal of which it is destined to become the food.
Soda appears to be a comparatively unimportant constituent of the ash,
of which it generally forms but a small proportion, although the
instances of its entire absence are rare. In the cruciferous plants
(turnip, rape, etc.) it is found abundantly, and to them it appears
indispensable, but in most other plants it admits of replacement by
potash. It seems probable that where the soil is rich in the latter
substance, plants will select that alkali in preference to soda; but as
they must have a certain quantity of alkali, the latter may supply the
place of the former where it is deficient. Cultivation, probably by
enriching the soil in that element, increases the proportion of potash
found in the ash of plants, as is remarkably seen in the asparagus,
which gave the following quantities of alkalies and chlorine:--
Wild. Cultivated.
Potash 18.8 50.5
Soda 16.2 trace.
Chlorine 16.5 8.3
The soda having almost entirely disappeared in the cultivated plant,
while a corresponding increase had taken place in the quantity of
potash.
Potash is one of the most important elements of the ash of all plants,
rarely forming less than 20, and sometimes more than 50 per cent of its
weight. The latter proportion occurs chiefly in the roots and tubers,
but it is also abundant in all seeds and in the grasses. The straw, and
particularly the chaff of the cereals, and the leaves of most plants,
contain it in smaller quantity, although exceptions to this are not
unfrequent, one of the most curious being the case of poppy-seed, which
contains only about 12 per cent, while the leaves yield upwards of 37
per cent.
The proportion of lime varies within very wide limits, being sometimes
as low as 1, and in other plants reaching 40 per cent of their ash. The
former proportion occurs in the grains of the cerealia, and the latter
in the leaves of some plants, and more especially in the Jerusalem
artichoke. The turnip and some of the leguminous plants also contain it
abundantly.
Magnesia is generally found in small quantity. It is largest in the
grains, amounting in them to about 12 or 13 per cent of the ash, but in
other plants it varies from 2 to 4 per cent. Although small in quantity,
it is an important substance, and apparently cannot be dispensed with;
at least there is no instance known of its entire absence.
_Chlorine_ is by no means an invariable constituent of the ash, although
it is generally present, and sometimes in considerable quantity. It is
most abundant when the proportion of soda is large, and exists in the
ash principally in combination with that base as common salt. The
relation between these two elements may be traced more or less
distinctly throughout the whole table of analyses, and conspicuously in
that of mangold-wurzel, where the common salt amounts to almost exactly
one-half of the whole mineral matter. The analyses of the cultivated and
uncultivated asparagus also show that a diminution in the soda is
accompanied by a reduction in the proportion of chlorine.
_Sulphuric Acid_ is an essential constituent of the ash. But it is to be
observed that it is in some instances entirely, and in all partially, a
product of the combustion to which the plant has been submitted in order
to obtain the ash. It is partly derived from the sulphur contained in
the albuminous compounds, which is oxidised and converted into sulphuric
acid during the process of burning the organic matter, and remains in
the ash. The quantity of sulphuric acid found in the ash is, however, no
criterion of that existing in the plant, for a considerable quantity of
it escapes during burning. The extent to which this occurs in particular
instances is well illustrated by reference to the case of white mustard,
which yields an ash containing only 2.19 of sulphuric acid, equivalent
to 0.9 of sulphur; and if calculated on the seed itself, this will
amount to no more than 0.039 per cent, while experiments made in another
manner prove it to contain about thirty times as much, or more than 1
per cent. For the purpose of determining the total quantity of sulphur
which the plants contain in their natural state, it is necessary to
oxidise them by means of nitric acid; and from such experiments the
following table, showing the _total_ amount of sulphur contained in 100
parts of different plants, dried at 212 deg., has been constructed:--
Poa palustris 0.165
Lolium perenne 0.310
Italian Ryegrass 0.329
Trifolium pratense 0.107
repens 0.099
Lucerne 0.336
Vetch 0.178
Potato tuber 0.082
tops 0.206
Carrot, root 0.092
tops 0.745
Mangold-Wurzel, root 0.058
tops 0.502
Swede, root 0.435
tops 0.458
Rape 0.448
Drumhead Cabbage 0.431
Wheat, grain 0.068
straw 0.245
Barley, grain, 0.053
straw 0.191
Oats, grain 0.103
straw 0.289
Rye, grain 0.051
Beans 0.056
Peas 0.127
Lentils 0.110
Hops 1.063
Gold of Pleasure 0.253
Black Mustard 1.170
White Mustard 1.050
_Phosphoric acid_, which may be looked upon as the most important
mineral constituent of plants, is found to be present in very variable
proportions. The straws, stems, and leaves contain it in comparatively
small quantity, but in the seeds of all plants it is very abundant. In
these of the cereals it constitutes nearly half of their whole mineral
components, and it rarely falls below 30 per cent.
_Carbonic acid_ occurs in very variable quantities in the ash. It is of
comparatively little importance in itself, and is really produced by the
oxidation of part of the carbonaceous matters of the plant; but it has a
special interest, in so far as it shows that part of the bases contained
in the plant must in its natural state have been in union with organic
acids, or combined in some way with the organic constituents of the
plant.
_Silica_ is an invariable constituent of the ash, but in most plants
occurs but in small quantity. The cereals and grasses form an exception
to this rule, for in them it is an abundant and important element. It is
not, however, uniformly distributed through them, but is accumulated to
a large extent in the stem, to the strength and rigidity of which it
greatly contributes. The hard shining layer which coats the exterior of
straw, and which is still more remarkably seen on the surface of the
bamboo, consists chiefly of silica; and in the latter plant this element
is sometimes so largely accumulated, that concretions resembling opal,
and composed entirely of it, are found loose within its joints. The
necessity for a large supply of silica in the stems of other plants does
not exist, and in them it rarely exceeds 5 or 6 per cent, but in some
leaves it is more abundant.
A knowledge of the composition of the ash of plants is of considerable
importance in a practical point of view, and enables us in many
instances to explain why some plants will not grow upon particular soils
on which others flourish. Thus, for instance, a plant which contains a
large quantity of lime, such as the bean or turnip, will not grow in a
soil in which that element is deficient, although wheat or barley, which
require but little lime, may yield excellent crops. Again, if the soil
be deficient in phosphoric acid, those plants only will grow luxuriantly
which require but a small quantity of that element, and hence it follows
that on such a soil plants cultivated for the sake of their stems,
roots, or leaves, in which the quantity of phosphoric acid is small, may
yield a good return; while others, cultivated for the sake of their
seed, in which the great proportion of that constituent of the ash is
accumulated, may yield a very small crop. It is obvious also that even
where a soil contains a proper quantity of all its ingredients, the
repeated cultivation of a plant which removes a large quantity of any
individual element, may, in the course of time, so far reduce the amount
of that substance as to render the soil incapable of any longer
producing that plant, although, if it be replaced by another which
requires but little of the element thus removed, it may again produce an
abundant crop. On this principle also, attempts have been made to
explain the rotation of crops, which has been supposed to depend on the
cultivation in successive years of plants which abstract from the soil
preponderating quantities of different mineral matters. But though this
has unquestionably a certain influence, we shall afterwards see reason
to doubt whether it affords a sufficient explanation of all the observed
phenomena.
It may be observed, on examining the table of the percentage and
position of the ash, that some plants are especially rich in alkalies,
while in others lime or silica preponderate, and it would therefore be
the object of the farmer to employ, in succession, crops containing
these elements in different proportions. In carrying out this view,
attempts have been made to classify different plants under the heads of
silica plants, lime plants, and potash plants; and the following table,
extracted from Liebig's _Agricultural Chemistry_, in which the
constituents of the ash are grouped under the three heads of salts of
potash and soda, lime and magnesia, and silica, gives such a
classification as far as it is at present possible:--
----------------------------------------------------------------------
| | Salts of | Salts of | Silica.
| | Potash and | Lime and |
| | Soda. | Magnesia. |
|----------------------------------|------------|-----------|---------
|Silica { Oat straw with seeds | 34.00 | 4.00 | 62.00
|Plants. { Wheat straw | 22.50 | 7.20 | 61.50
| { Barley straw with seeds| 19.00 | 25.70 | 55.30
| { Rye straw | 18.65 | 16.52 | 63.89
| { Good hay | 6.00 | 34.00 | 60.00
|Lime { Tobacco | 24.34 | 67.44 | 8.30
|Plants { Pea straw | 27.82 | 63.74 | 7.81
| { Potato plant | 4.20 | 59.40 | 36.40
| { Meadow Clover | 39.20 | 56.00 | 4.90
|Potash { Maize straw | 72.45 | 6.50 | 18.00
|Plants. { Turnips | 81.60 | 18.40 | --
| { Beet root | 88.00 | 12.00 | --
| { Potatoes | 85.81 | 14.19 | --
| { Jerusalem Artichoke | 84.30 | 15.70 | --
----------------------------------------------------------------------
The special application of these facts must be reserved till we come to
treat of the rotation of crops.
It is manifest that, as the crops removed from the soil all contain a
greater or less amount of inorganic matters, they must be continually
undergoing diminution, and at length be completely exhausted unless
their quantity is maintained from some external source. In many cases
the supply of these substances is so large that ages may elapse before
this becomes apparent, but where the quantity is small, a system of
reckless cropping may reduce a soil to a state of absolute sterility. A
remarkable illustration of this fact is found in the virgin soils of
America, from which the early settlers reaped almost unheard-of crops,
but, by injudicious cultivation, they were soon exhausted and abandoned,
new tracts being brought in and cultivated only to be in their turn
abandoned. The knowledge of the composition of the ash of plants assists
us in ascertaining how this exhaustion may be avoided, and indicates the
mode in which such soils may be preserved in a fertile state.
FOOTNOTES:
[Footnote A: Apparently a species of Sinapis.]
[Footnote B: Oxide of Manganese, 0.42.]
[Footnote C: Oxide of Manganese, 0.92.]
[Footnote D: Alumina, 1.02.]
[Footnote E: Alumina, 0.63.]
[Footnote F: Iodide of Potassium, 0.44; Sulphuret of Sodium, 3.66.]
[Footnote G: Iodide of Potassium, 0.23.]
[Footnote H: Iodide of Potassium, 1.68.]