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THE STRANGE TALE 



OF SO,+ H,0=H,SO 



Here's hozv smoke and fog work to the injury of plants in greenhouses, 

 setting up a chemical reaction which forms an acid that burns the leaves. 

 Read this article and it probably will make clear to you certain things which 

 have been a mystery and the cause of money loss. 



ml 





OV all know what it does to 



^C T" your stock to burn sulphur 



<Qx^^ ill the greenhouses, especi- 



y I ally if the foliage or even 



' the atmosphere is damp at 



the time — it makes the 



leaves look as though they 



had been exposed to a blast 



of air that was scorching 



hot. It is because the blue 



fliuiic of the sulphur is liberating a auf- 



t'ocatiug gas, sulphur dioxide. 



A good inauy growers have for years 

 ii()te(l a similar, if milder, injury to their 

 stock at times when they had not been 

 using sulphur or any other fungicide 

 and for which they were unable to ac- 

 count. Tn the last year or so the re- 

 jiorts of such damage have become more 

 numerous, with the result that an in- 

 vestigation has determined that the in- 

 crease noted is the direct result of the 

 war with Germany, the strange tale of 

 SO, -+- H,0 -. H,SO,. Read on if you 

 would know. 



Fundamental Facts. 



Comparing the known 

 facts in the numerous 

 cases of plant injury un- 

 der study, it was found 

 that all i)resented cer- 

 tain aspects in common. 

 >'iist, they showed the 

 kind (if injury with 

 wliich most gardeners 

 •'lie familiar as arising 

 from tlie presence of sul- 

 phur in the air, either 

 outdoors or under glass: 

 •^'■cond, tliey all were re- 

 l>orted from localities 

 ■TlJacent to industrial 

 '•enters, never from the 

 "I'Pii country; third, the 

 '"iinlicr of cases of in- 

 .l>iiy increased greatlv 

 witl.ui the last vear, 

 iitter war work began to 

 '•'111 the factories night 

 •■'lid day; fourth, the 

 '''""age almost alwavs 

 |vas not<.d on davs fol- 

 '"\\'»S: deuselv * foggv 

 "lorninjjs, such' as those 

 " February 22 and 

 •March r, and 8 at Chi- 

 '"«(., when the air was 

 '"'avy and "low." 



These facts led un- 

 ""stakably to the con- 

 ' '"^'"11 that there was a 

 """lection between the 

 ^'"oke and the injury of 

 ,'"' plants and a little 

 ' " rth er investigation 

 flowed that, while the 

 '''""age had been noted 



By WILLIAM J. O'CARROLL 



Clilef (iardener. 

 lliilverslty of ChlcaKro Botanical (iardens. 



for years in such communities as Chi- 

 cago and Pittsburgh, where smoke is 

 dense, this particular injury to stock in 

 greenhouses had been observed for the 

 tirst time this year in localities which 

 heretofore had used anthracite prin- 

 cipally, but which, because of war con- 

 ditions, had been forced to resort to 

 bituminous coal for this season. 



Mustard Gas. 



8o it was apparent that the loss per- 

 ])lexing growers could be traced direct- 

 ly to the soft coal smoke. The plants 

 were gassed. But it was "mustard" 

 gas, for it burned. 



Growers have noted that sulphur gas, 

 always injurious to plants, is at its 

 worst when plants or atmosphere are 

 moist; then the burning is most severe. 

 Also it was noted that on the foggy 



Cineraria Gasied by Sulphur Dioxide on a Smoky Morning. 



mornings, when the clouds hung low, 

 the burning of foliage was greatest 

 where the hose was used. 



It worked out this way: Bituminous 

 coal contains a considerable percentage 

 of sulphur. The burning of thousands 

 upon thousands of. tons of sulphurous 

 coal liberated great quantities of sul- 

 ])hur dioxide. The fog and clouds held 

 this gas close to earth, suspended in 

 the air, instead of its floating away, as 

 it would do in a bright, clear day. When 

 sulphur dioxide is combined with water 

 it forms sulphurous acid, which will 

 burn the leaves of plants. This is the 

 chemical equation: S02-|-H;0=HjS03. 



In certain cases material damage has 

 been caused in this manner, to the com- 

 plete mystification of the grower, who 

 could see no cause for the perfectly ap- 

 parent burning of his plants going on 

 under his very eyes. Large numbers of 

 chrysanthemums were ruined by this 

 cause in the autumn of 1917 and the 

 growers in most cases said they had 

 ' 'damped off." 



Preventive Measures. 



Monocotyledonous 

 jdants are most suscep- 

 tible to this gas and acid 

 injury and begonias, 

 cinerarias, primulas, ste- 

 vias, ferns, orchids and 

 tomatoes are among 

 those likely to show first 

 the effects. Plants with 

 a large number of sto- 

 mates are among those 

 most likely to be injured. 

 Conversely, those species 

 liaving few stomates will 

 sustain the conditions 

 described with the mini- 

 mum damage. 



The man in charge of 

 a greenhouse should be 

 alert to jirevailing con- 

 ditions. He should not 

 admit gas unnecessarily 

 by opening ventilators 

 ()r otherwise, bearing in 

 mind that the gas will 

 do more damage than 

 the lack of air. 



Here are three points 

 T have worked out and 

 which also have been 

 tested on a large scale, 

 and successfully, by 

 August Koch, in charge 

 of the famous conserva- 

 tories in Garfield park, 

 Chicago: 



First, reduce the tem- 

 perature of the houses 

 10 degrees or more; sec- 

 ond, keep all ventilators 



