128 



THE FLORAL WORLD AND GARDEN GUIDE. 



a l\icfc we can easily show : if you breathe 

 through a tube or pipe, so that the air 

 as it leaves the lungs passes through a 

 solution of lime, it will render it milky or 

 turbid from the formation of carbonate of 

 lime. The solution of lime is a very good 

 test for the presence of this substance, as 

 it always renders the clear solution milky, 

 as I have shown. 



Carbonic acid gas is much heavier than 

 atmospheric air, hence it sometimes accu- 

 mulates in wells and other places, where 

 the stagnant condition of tlie air allows it. 

 If we examine the leaf of a plant, we 

 shall find it covered with minute pores or 

 mouths, through which it absorbs this gas 

 and other substances necessary for its de- 

 velopment. The number of these pores is 

 wonderful ; on a single square inch of the 

 lilac as many as 120,000 have been counted, 

 and the rapidity with which they act is so 

 great, that a thin current of air in passing 

 over the leaves of an actively growing 

 plant is instantly deprived of the carbonic 

 acid it contains. We thus see that it is no 

 longer a wonder tliat the oak, with from 

 live to ten millions of leaves, is capable of 

 secreting so large an amount of carbon ne- 

 cessary for its growth. But plants not 

 only absorb carbonic acid, but decompose 

 it. The manner in which this is done is 

 not yet known, but the fact is certain, that 

 for every twenty-two pounds of carbonic 

 acid absorbed by the plant sixteen pounds 

 of pure oxygen is given off. So we see 

 a most beautiful arrangement, that what 

 is rendered unfit for man and all animal 

 life, is restored to its pure condition, and 

 fitted to be again inhaled, by the action of 

 the leaves of plants. But it may be 

 asked how do plants derive their carbon 

 which have no leaves or foliage, such as 

 bulbs ? or in the case of seeds, how do 

 they derive their carbon ? Tliis is easily 

 explained. In the bulb of a tulip or 

 hyacinth we have an accumulation of 

 food, which supplies it with nutriment till 

 it can derive it from the foliage. In the 

 other case of seed, we know that most 

 seeds contain a large portion of starch, 

 which is rendered fit for the nutrition 

 of the embryo plant by a substance called 

 by chemists dextrine, which has the pro- 

 perty of changing the starch of seeds to 

 sugar. We know that this is applied in 

 the process of malting. The starch con- 

 tained in the barley is converted into 

 sugar by allowing the barley to lie in 

 heaps till, with tlie aid of moisture and 

 heat, it begins to gei'minate. It is then 

 dried in kilns, which prevents its further 

 growth. We thus see a beautiful ar- 



rangement by which the starch, which of 

 itself is insoluble, and therefore not fit to 

 nourish the plant, is rendered soluble 

 when the growth of the embryo requires 

 it. But there are other elements in plants 

 besides carbon and water : all plants bear- 

 ing seeds or flowers contain nitrogen. This 

 gas is, as we have said before, one of the 

 constituents of the atmosphere : but it does 

 not appear from recent researches that the 

 nitrogen of plants is derived from that 

 source, but from a substance which exists 

 in the atmosphere called ammonia. But 

 in horticulture we require an increased 

 supply of food, as in the increase of the 

 flowers we must have an increase in the 

 materials which form them. Ammonia 

 is derived from the decomposition of all 

 animal matter ; the duug and urine of all 

 animals contain it in large quantities ; 

 other substances also yield large quantities, 

 such as the salts of ammonia, soot. The 

 proportion of ammonia contained in 1000 

 parts of each of those substances may be 

 definitely ascertained. 



In a free state, ammonia is a gas, invi- 

 sible and colourless, but possessed of a 

 powerful, irritating smell. In its pure 

 state it is so powerful as to be injurious 

 and destructive to life. It is extremely 

 volatile, as it flies off" as soon as produced. 

 Tlie liquid sold as spirits of hartshorn is 

 ammonia dissolved in water. Ammonia 

 unites with most acids, forming salts, as 

 carbonate of ammonia, or smelling salts, 

 a substance much used in the manufacture 

 of bread and biscuits. With hydrochloric 

 acid it forms hydrochlorate of ammonia, 

 or sal ammoniac, a very powerful and 

 useful fertilizer. With nitric acid it forms 

 nitrate of ammonia, another equally good 

 manure ; and witli sulphuric acid it forms 

 the sulphate of ammonia : each of these 

 have been applied with great success as 

 means of supplying ammonia to plants. 

 Ammonia cannot be applied in its pure 

 state as a manure, on account of its ex- 

 treme volatility, as it would, if applied in 

 that state, quickly evaporate in the air, 

 and be lost ; to avoid this loss in dung heaps 

 or reservoirs of urine, or any materials 

 generating ammonia, it is desirable to fix 

 it, as it is termed. This is easily done by 

 the addition of any cheap mineral acid, 

 such as sulphuric or hydrochloric acid, 

 which unites with it, and forms salts which 

 are more stable or fixed in their character. 

 Lime decomposes all the salts of ammonia, 

 combining with the acid they contain, and 

 liberating the free ammonia ; therefore lime 

 or lime water ought not to be applied at 

 the same time as any manure containing 



