244 



THE GARDENER'S MONTHLY 



\Augusty 



no means fixed, but that they do so to an extent 

 whereby they can be fertilized or invigorated so 

 as to give any practical assistance in their cul- 

 ture by being stimulated with ammonia or nitro- 

 gen applied to the leaves only, I yet very much 

 doubt. 



Mr. Milton says that the reason that vegetation 

 in the immediate vicinity of bone factories, etc., 

 is not improved by the exhalations therefrom is 

 because it is not in condition to be absorbed. 

 Why not ? If the open air is charged with ammo- 

 nia in a rainy or moist day, in what way does it 

 differ from Mr. Foust's greenhouse vvhei-ein he 

 lets loose the ammonia from his heated shovel ? 

 If the one case fails to fertilize vegetation cer- 

 tainly the other must, for we know from the 

 unpleasant odors wafted for miles that in the 

 immediate vicinity of such factories the air 

 must be pregnant with the gases that go to feed 

 plants, and that when carried down by the rains 

 to the leaves, and no beneficial result follows, 

 — and it certanly never does — this evidence 

 goes far to deny the generally received opinion 

 that plants can be fed through their leaves. 



Mr. Foust's prescription would have inspii'ed 

 more confidence if he could have stated that the 

 "improvement" he claims was shown from a 

 comparative test. I have no doubt the plants 

 and llowers in his careful hands showed well 

 even after such an application, but is he sure 

 without comparison that this was the result of 

 the air being charged with ammonia? It is not 

 an unusual practice for doctors to prescribe bread 

 pills to their patients ; may be it would be better 

 if nothing else were ever prescribed. The patients 

 improve and of course the pills are given the 

 credit. Mr. Foust's ammonia, as he says, cer- 

 tainly does no harm ; neither do the bread pills ; 

 but do either do any good? They may, but I 

 won't believe it until Mr. Foust can show that 

 under exactly similar conditions of the same 

 kinds of plants, grown in the same soil, tempe- 

 rature and moisture, that one greenhouse treated 

 to the ammonia shows better results than 

 another alongside without it. Any such trial as 

 he describes, made without comparison, is never 

 satisfactory and is always open to question. 



PLANT LEAVES AND THEIR FUNCTIONS, 

 RESPIRATION AND EXHALATION. 



BY J. GRIEVES, PATERSON, N. J. 



In Mr. Peter Henderson's article in the June 

 number of the Gardeners' Monthly he says : 

 " My practice, which has extended through a pe- 



riod of over thirty-five years, and which I believe 

 has been as varied and extensive as that of most 

 men in that time, has never yet shown me a sin- 

 gle instance wherein I was certain that plants 

 either absorbed liquid manure, or even fertiliz- 

 ing gases by their leaves." My experience in 

 plants has not been as long and varied as it 

 might have been ; but in chemistry I have dab- 

 bled more, and would modestly suggest to him 

 or others interested, a very simple and effec- 

 tive test in regard to the absorption of fer- 

 tilizing gases by the leaves of plants, which I 

 believe will prove the fact to a certainty. Take 

 a bell glass and fill it with water, to which a 

 considerable proportion of carbonic acid gas has 

 previously been added, and place in it a branch 

 or an entire plant covered with leaves, and ex- 

 pose the whole to the rays of the sun for some 

 hours. The air if now analyzed will be found 

 to contain scarcel}'^ any carbonic acid gas, but it 

 will contain a larger proportion of oxygen than 

 before the experiment. Now if we take a 

 branch of a plant with the roots fixed and grow- 

 ing in the soil,— consequently in its normal state 

 of vegetation, — and place it in a glass vessel, and 

 by means of an air pump a given quantity of air 

 is caused to circulate round it, this air which be- 

 fore the experiment contained from four to five 

 ten-thousauth parts of carbonic acid gas, aftei- 

 the apparatus has been exposed to the sun^s 

 rays for a certain time, will not be found to con- 

 tain more than from one to two. If on the con- 

 trary the experiment is made during the night 

 it will be found that the quantity of carbonic 

 acid gas would be increased, and at the expira- 

 tion of a certain time would have risen to eight 

 ten-thousanth parts. If we now reverse our first 

 experiment and put a pliant or leafy branch in a 

 jar or balloon with gas which cannot be renewed 

 and leave the whole in darkness for some ten to 

 fifteen hours, we may assure ourselves at the 

 end of this time that the atmospheric air con- 

 tained in our vessel is no longer of the same 

 composition as before the experiment. Car- 

 bonic acid will now be there in greater abun- 

 dance and the quantity of oxygen will be less. 

 But if in place of leaving the plant in darkness 

 we expose the apparatus to the sun's rays, the 

 balloon or jar will have lost a noticeable quan- 

 tity of its carbonic acid gas and will be enriched 

 in its oxygen. 



These experiments, in which there is an inter- 

 change of gas between the plant and the atmos- 

 phere, exhibit the doable phenomena of absorp- 



