THE GASES PLANTS FEED UPON. 



moist atmosphere, until the plants are in flower, when it should be dry; at this stage the 

 heat by night should never be more than 50''; pass the hand gently over the trusses of 

 bloom, to assist in the diffusion of the pollen. After the fruit is set, the heat may be rais- 

 ed from G0° to 70''; water every alternate watering with liquid manure, while in bloora, 

 and the fruit swelling; when in bloom all the small flowers should be picked off to about 

 six to a truss, and when fairly set these should be reduced to three or four, which will 

 be sufficient to a truss; syringe them frequently, except when in flower; when the least 

 sign of green fly is perceptible, fumigate; as the fruit approaches maturity discontinue 

 water; keep a dry atmosphere, with as much sun-light and air as possible, to enhance 

 flavor. Cuthill's Black Prince, Keen's Seedling, and British Queen, are about the best for 

 this purpose. J. S. 



Washington, Nov. 2, 1851, 



■*-*-¥ 



THE GASES PLANTS FEED UPON. 



BY DR. LINDLEY. 



Plants play a very important part in the economy of the creation; for, independent 

 of their relation to animals as the real source of all food, they are essential to the purity 

 of the air. We are told by chemists, that the composition of the atmosphere is quite con- 

 stant and uniform; that air, from whatever place it is collected, is always found to con- 

 sist of the same proportions of oxygen and nitrogen and carbonic acid. This fact has 

 now been established by a number of careful experiments, made by different observers, in 

 various parts of the globe, and extending over a considerable period of time, so that it 

 may in fact be considered as proved, not only that the composition of the air is uniform 

 throughout, but also that it does not undergo any appreciable variation in nature from 

 year to year. There is certainly something very wonderful in this, and indeed it seems 

 difficult to understand how it really can be the case, when we observe the great chemical 

 changes which are at all times going on in the atmosphere, and the enormous quantities 

 of certain substances which are constantly being poured into it in various ways. Night 

 and day all living animals are consuming the oxygen of the air, converting it into carbonic 

 acid, and the same effect is also constantly being produced all over the earth, by fires, 

 furnaces, lamps, candles, and in short by combustion in all its forms. Decay, putrefac- 

 tion, and fermentation, are also giving rise to the evolution of carbonic acid; and lastly, 

 besides all these sources, immense quantities of the gas in question are evolved from fis- 

 sures in the earth, especially in what are termed volcanic districts. There are then, to say 

 nothing of smaller or more local causes, at least half a dozen great natural operations, all 

 tending to vitiate the air, diminishing the quantity of oxygen which it contains, and in- 

 creasing the proportion of carbonic acid. All these causes, we are told, are exactly 

 balanced and neutralised by the decomposing influence of plants, and the wonderful power 

 -which they have of absorbing the carbon of carbonic acid. We owe this remarkable fact 

 to the researches of Drs. Priestley and Ingenhousz, extended, repeated, and confirmed 

 by a host of other observers. 



In Dr. Priestley's first experiments on carbonic acid or fixed air, it is evident that he 

 regarded it as highly poisonous to plants; for in the first volume of his very interesting 

 Essays on Air, he says — " Fixed air is presently fatal to vegetable life;" and he goes on 

 to show that plants, in many cases, were very soon killed, when exposed to the influence 

 of carbonic acid gas, collected from the fermenting vat of a brewery: he however observes, 



