226 



JOURNAL OP HORTICULTURE AND COTTAGE GARDENER. 



[ March at, 1870. 



above mentioned." This property, therefore, of ammonia must, 

 I consider, be more important than that of supplying the plant 

 with nitrogen. 



There is also another very valuable property in ammonia, 

 and that is that it supplies the plant with hydrogen. This 

 property is much overlooked, because many persons argue that 

 as there is so much hydrogen in water, which forms so great a 

 bulk by weight in any plant, the plant can obtain as much 

 hydrogen as it requires from that. Moreover, most agricul- 

 tural chemists state that water is easily decomposed by plants, 

 and then the elements are re-arranged to form water. I 

 cannot see any proof or any strong grounds on which this 

 statement restB. Water, as is well known, is the product of the 

 combustion of hydrogen in oxygen, and when once formed is 

 one of the most stable and most neutral ingredients known. It 

 is this property which makes it so valuable to analytical 

 chemists ; it has the power of holding so many different sub- 

 stances in solution without chemically altering their nature, 

 and when the water is evaporated the substances remain the 

 same as before. It has, however, the power of combining as a 

 base with many substances. Thus, if a solution of sulphuric 

 acid and water is distilled, the water is given off first in the 

 shape of steam, but after a timo sulphuric acid distils over with 

 the steam, and it is found impossible to separate any more 

 water from the acid . This portion of water which combines with 

 the acid is called a base, and the substances so formed are 

 called hydrates ; but in all these cases the proportion of 

 hydrogen to oxygen remains unchanged. A strong instance of 

 this may again be pointed out in those very substances which 

 I have before alluded to — gum, sugar, starch, mucilage, &e., 

 and the humic acid group, all of which may be considered as 

 hydrates of carbon, as the relative proportions of hydrogen and 

 oxygen found in them are the same as in water. It is only by 

 powerful chemical means that the hydrogen is separated from 

 the oxygen. Thus, if the two platinum plates are dipped in 

 water and connected together by the wires of a strong electric 

 battery, bubbles of gas will be seen to rise from each of the 

 platinum plates. If these are collected by means of glass 

 receivers, one of the gases will be found to be hydrogen, the 

 other oxygen. Or, again, hydrogen may be separated from 

 water by the action of nitric or sulphuric acid upon zinc in 

 water. Water is, however, by no means easily decomposed, 

 although it helps to decompose vegetable substances as soon as 

 they are deprived of life ; but I cannot see any proof that those 

 compounds which contain an excess of hydrogen in plantB, can 

 easily obtain what they require from water. 



To refer, however, once more to the analyses of different 

 vegetable substances which I mentioned in my last paper, as 

 Wheat, both grain and straw, hay, Turnips, See., after all free 

 water has been expelled, by drying at a heat of 212°, there 

 remains an excess of hydrogen, generally from 5 to 6 per cent, 

 of the weight of the plant, and as hydrogen is the lightest 

 known substance, it is considerably greater in bulk. This 

 hydrogen is one of the ingredients supplied to the plant by 

 ammonia, because as all compounds of nitrogen are easily de- 

 composed, the hydrogen from ammonia (N H3), is freely given 

 off. Hydrogen has been found by experiment to be one of the 

 most important ingredients in the colouring matter of leaves, 

 and it is most probably this property in ammonia which helps 

 to impart the dark, rich green colour to growing crops that are 

 watered with liquids containing ammonia in solution. It not 

 only, that is to say, enables the plant to grow more quickly by 

 acting as a solvent to the vegetable constituents of the soil, but 

 it supplies it also with the hydrogen which is always found in 

 growing crops. 



Ammonia is generally found in the form of carbonate of 

 ammonia, as it readily combines with carbonic acid ; and 

 whether the ammonia arises from the decomposition of vege- 

 table or animal matter, carbonic acid, with which it unites, is 

 almost always given off at the same time. Carbonate of am- 

 monia is almost always found in rain water. Liebig attributes 

 this to the evaporation of ammonia from decomposing organic 

 matters which rises into the air, and is then brought down in 

 solution by the rain ; but independently of the fact that there 

 is so slight a portion of ammonia present in the air that it is 

 almost impossible to trace it, he overlooks one way in which 

 carbonate of ammonia may easily be generated in the clouds, 

 because the different substances of which it is formed are all 

 present in the cloud, and there is also an amount of electrical 

 action, which is always favourable to the formation of such 

 compounds. Thus we have aqueous vapour, which contains 

 the hydrogen, carbonic acid, and nitrogen, all in a finely sub- 



divided state, and intimately mixed together in the upper 

 strata of the air ; and as the rain which falls contains oarbouate 

 of ammonia, it is only fair to infer that small portions of am- 

 monia may be formed in this way by the action of electricity 

 in the clouds ; and as the softness and solvent power of soft 

 water are due greatly to its ammonia, it may be that these im- 

 portant properties are derived directly from the clouds them- 

 eelves. It is a pretty generally received opinion that the traces 

 of nitric acid (N O5), which are found in the atmosphere, are 

 formed by the union of one part of nitrogen to five of oxygen 

 by means of lightning, because nitric acid has been experi- 

 mentally formed by the same means, by passing electric flashes 

 through a jar filled with air. 



I have already alluded, in my last paper, to the property of 

 nitrate of soda, in increasing the straw by acting as a sol- 

 vent to the silicon ; I need not, therefore, add more to the 

 argument I there adduced to prove that nitrate of soda was 

 more valuable as a manure by its increasing the bulk of the 

 Btraw than for adding nitrogen to the grain, especially as it 

 is generally found that, though nitrate of soda may increase 

 the bulk, it does not improve the quality of the grain. More- 

 over, in estimating the value of nitrogen in the grain of Wheat, 

 there is more in the husk or bran than in the flour, and those 

 grains which are most rich in nitrogen are generally coarser in 

 the husk. 



To sum up, then, in a few words : Until I can have some 

 proofs brought forward to the contrary, I believe that nitro- 

 genous manures are valuable, not because of the nitrogen they 

 contain, but because they are of themselves more easily 

 decomposed, and also (which is a point I have not hitherto 

 entered upon) they are generally of a complex form, and oon- 

 tain a great number of different saline and other ingredients 

 necessary to the welfare of plants. Take, for instance, guano, 

 which contains, besides ammonia, phosphate of lime, phos- 

 phate of soda, and phosphoric acid. Next, I believe, that 

 plants can absorb from the atmosphere whatever nitrogen they 

 may require, but that in most plants it is so small that it still 

 deserves the name which chemists originally gave it, of azote, 

 or a non-supporter of life, and that it is quite contrary to the 

 usual ways of Providence to put a plant in a medium necessary 

 for its existence, and yet forbid it the power of assimilating it 

 fer its own use. And I conclude by saying I think the reason 

 why a fictitious value has been given to nitrogen is, because 

 ammonia, a compound of nitrogen, has always been found of 

 such value in manures, but that the real value of ammonia is 

 owing to its being a solvent for the organic compounds for the 

 soil, and also for the hydrogen which it supplies ; it is also 

 valuable as combining with other mineral ingredients of the 

 soil, and presenting them in a soluble form to theroot3 through 

 the sap ; and that this property is far more valuable than the 

 property it may possess of supplying nitrogen. I can hardly 

 expect, perhaps, to convince others ; I only wish to be con- 

 vinced myself that I am wiong, and shall be very glad if any 

 persons who are more conversant with the subject than I am 

 will show where my arguments fail. I may he told I have not 

 reflected enough ; but 1 have not put these opinions of my 

 own forward without looking over carefully all the proofs which 

 Liebig and Johnston bring forward of the value of nitrogen, 

 and cannot but think that the value of nitrogen has been im- 

 mensely exaggerated, and that this supposed value of nitrogen 

 began from the broad and direct assertion of Liebig, which he 

 afterwards argued from as an established fact. — C. P. Peach. 



THE DIFFUSION OF PLANTS. 

 In the new periodical, Nature, it is Btated that Professor 

 Delpino, of Florence, has published some interesting researches 

 on the relation between the diffusion of plants and animals. 

 The life of every plant has three principal objects : its nourish- 

 ment, its reproduction, and the distribution of its seeds ; for 

 each of these three objects special biological conditions being 

 requisite. The fertilisation of many plants can be effected only 

 by some particular animal; as Arum italicum, Aristolochia, 

 and Asarum, by gnats ; the Fig tribe by different species of 

 Cynips (or gall fly) ; Arum Dracunculus, Scapelia, and Rafflesia, 

 by blue-bottle flies ; many others by different kinds of flies or 

 bee-like insects (Hymenoptera), and some even by small birds 

 belonging to the family of Trochilidffi, or humming birds ; 

 Rosa, Pteonia, and Magnolia yraudiflora, by beetles of the 

 chafer tribe ; others again by small slugs. If in any particular 

 locality the animal necessary for the fertilisation of a particular 



