Decomposition of Ammonia.—The nitrogenous or albuminous compounds of vegetables must necessarily obtain their nitrogen from the decomposition either of ammonia or nitric acid, experiment having distinctly shown that they are incapable of absorbing it in the free state from the atmosphere. It has been clearly ascertained that the albuminous substances do not contain ammonia, and it is hence apparent that a complete decomposition of that substance must take place in the plant. No doubt carbonic acid and water take part with it in these changes, which must be of a very complex character, and in the present state of our knowledge it seems hopeless to attempt any explanation of them.
Decomposition of Nitric Acid.—Chemists are not entirely at one as to whether nitric acid is directly absorbed by the plant, or is first converted into ammonia. But there are certain facts connected with the chemistry of the soil, to be afterwards referred to, which seem to us to leave no doubt that it may be directly absorbed; and in that case it must be decomposed, its oxygen being eliminated, and the nitrogen taking part with carbon and hydrogen in the formation of the organic compounds. It must be clearly understood that while such changes as those described manifestly must take place, the explanations of them which have been attempted by various chemists are not to be accepted as determinately established facts; they are at present no more than hypothetical views which have been expressed chiefly with the intention of presenting some definite idea to the mind, and are unsupported by absolute proof; they are only inferences drawn from the general bearings of known facts, and not facts themselves. Although, therefore, they are to be received with caution, they have advantages in so far as they present the matter to us in a somewhat more tangible form than the vague general statements which are all that could otherwise be made.
CHAPTER IV.
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°. 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°.
| 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 |