1879. 



AND HORTICULTURIST. 



185 



any hotbed formed of dun<;, and yet we know 

 that the exhalations from tan bark are not likely 

 to contain either ammonia or nitrogen. The 

 famous Boston hotbed-grown lettuce, by which 

 our New York markets were almost exclusively 

 supplied ten years ago, now finds a formidable 

 rival in the lettuce grown in greenhouses, hund- 

 reds of which, covering many acres are now in 

 use for that purpose in nearly every Northern 

 State. Budlong & Co., Providence, R. I.; Abra- 

 ham Van Sicklen, Jamaica, L. I.; Mabbitt «fe 

 "Wills, of Riverton, N. .J., and Muir Bros, of 

 Newark, N. J., are all extensive greenhouse 

 growers of lettuce for the New York market ; 

 and I am informed by a leading commission 

 dealer, who sells for the two firms first named 

 that their lettuce now far exceeds in quality the 

 hotbed-grown Boston lettuce, though no manure 

 in any shape is used except at the roots. My 

 belief is, that it is the uniformly proper condi- 

 tion of moisture that we get in a dung hotbed, 

 that gives us the luxuriance of growth, for when 

 we produce the same conditions in the atmos- 

 phere of the greenhouse, we know that we at- 

 tain equally good results. That leaves absorb 

 moisture from the atmosphere is so generally a 

 received opinion that when I question its truth, 

 I well know that I am trenching on dangerous 

 ground, but let us examine. If we take a plant 

 from a greenhouse that is kept continuall}^ 

 charged with moisture and place it for a few 

 hours in a dry room its leaves begin to wilt and 

 droop. Now the believer in the moisture-absorb- 

 ing theory will say that this is because it has 

 not sufficient moisture in the dry air for its sus- 

 tenance, but is it not just as easy to suppose 

 that it is because the plant evaporates its moist- 

 ure in a dry atmosphere, while it would not do 

 so in a damp one ? Or in other words the moist 

 air acts only as a negative benefit, preventing 

 the evaporation of the moisture from the leaves 

 which has been taken from the soil by the roots. I 

 believe that you can no more feed a plant through 

 its leaves, than you can feed man, or any other | 

 animal, for any length of time through the ■ 

 pores of the skin, and that it is from the roots ' 

 and root onl}-, in plants that absorption can ■ 

 take place to any noticeable extent. 



In experimenting on this subject a few j 

 years ago I suspended two large stems of Cac- \ 

 tus triangularis and C. grandiflonis, in a moist I 

 stove, weighed them when put in, and at the I 

 end of six months weighed them again, and 

 though they kept fresh and green, they liad 



neither increased nor diminished in weight, 

 though the air was pregnant with moisture and 

 often ammonia too; for we use liquid manure 

 largely in all our greenhouse operations, but we 

 use it at the roots only, and if by chance it gets 

 on the leaves we at once wash it off" with the 

 hose, believing it to be injurious rather than 

 otherwise, in clogging the pores. 



Whwi a boy, I was for some time clerk in a 

 liquor store in the city of Edinburgh. When 

 whiskey was sent to us from the distilleries it 

 had to be pumped out of the puncheons into 

 smaller kegs for distribution. On every pump- 

 ing day our old Highland porter invariably got 

 drunk, but he always protested he was a victim 

 of circumstances, a martyr to duty ; the smell 

 from the whiskey made him "light headed." It 

 was imagined for some time that Donald might 

 have been so constituted that the fumes affected 

 him and no one else, but we had him watched, 

 and found as we had before suspected, that he 

 was taking his stimulant through his mouth to 

 his stomach ; so I rather suspect it will be found 

 in all such cases as Professor Riley alludes to, 

 that when plants are supposed to be stimulated 

 by application of liquid manure to the leaves, 

 that enough may have run from the leaves to 

 the roots, the stomach (?) of the plant, to stimu- 

 late growth. 



[We offered the hotbed observations not as 

 direct proof, but as collateral evidence. As to 

 the main point, can plants absorb and digest 

 nitrogenous matter through their leaves? We 

 know they do so use carbonic acid in that way, 

 and there is nothing therefore impossible in 

 their using other elements in like manner and 

 that they really do use nitrogen through their 

 leaves we think is made a certainty to most 

 persons who will carefully study Mr. Darwin's 

 facts as given in "Insectivorous Plants."] 



EXPERIMENTS IN CR OSS-B R E E D I N C 

 PLANTS OF THE SAME VARIETY. 



BY PROFESSOR W. J. BEAL. 



The folloAving article we copy from the Ameri- 

 can Journal of Science and Arts for May. It 

 formed iiart of Professor Beale's lecture given 

 last Winter before the farmers' institutes. Witli 

 reference to it, Prof. A. Gray, of Harvard 

 University, writes that "the experiments are 

 very neat and to the purpose," and then he 

 gives the article the place ol honor in the jour- 

 nal of wliieli lie is one of the associate editors. 



