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1884.) The Exhalation of Ozone by Flowering Plants. 343 
Schoenbein gave only three “very slight” reactions. During 
these observations the outer air was tested twelve times, with but 
two“ slight” reactions, and the air of the propagating house for the 
remaining days in place of the outer air, which gave two “ very 
slight” reactions. The air of the propagating house was next 
compared with the external air. For thirteen days in the former 
situation the Schoenbein paper gave “very slight” reactions in 
four instances, while the latter (outer air) gave “ very slight” in- 
dications of ozone in two instances. It will be observed that here 
the result was better in the propagating house than in the open 
air, which was, to say the least, quite suggestive. In all the pre- 
ceding experiments of this series there was a striking similarity 
in the two situations, and the outer air giving somewhat the bet- 
ter results. The air of the fern house, as well as economic house, 
were also given a few trials and compared with the outer air, but 
the results were negative throughout. During all of the out- 
door observations the guaiacum paper gave slight indications of 
ozone in more than half of the experiments, and striking in four 
cases. The results with this paper for corresponding days in- 
doors were almost identical, with the degree of coloring in a few 
instances in favor of the outside. The propagating house yielded 
the best indoor results with the guaiacum paper, as did the 
Schoenbein, while the temperate house gave almost equally good 
results with the guaiacum paper as in the propagating house. 
$ was not the case, it will be remembered, with the Schoen- 
bein, The duration of the individual experiments varied from 
SIX to sixteen hours, the average duration being about ten hours. 
; The question here arises, were the reactions obtained by the 
indoor tests due to ozone emitted from the plants or to the circu- 
lation of the outer air through these apartments. There is. con- 
_ Santly more or less interchange of air between the exterior and 
a of the building, due to the numerous interstices between 
panes of glass and the frequent opening and closing of the 
| heated “a must also be observed that all these apartments are 
and artificial heat was necessary during all these investi- 
by numerous hot water pipes placed directly under and 
Parallel with a grated floor from which warm air rises and ascends 
through the building. The idea that the external conditions 
might bs affected the results on the inside is doubtless still fur- 
Strengthened by the fact that most of the results obtained 
