1885. ] The Exhalation of Ozone by Odorous Plants. 861 
function is so actively carried on by odorous flowers, it oc- 
curred to us to make a trial of plants whose leaves emit odors 
but having no flowers.. Blooming geraniums having been ex: 
perimented with while making previous researches into the 
same subject, and having found them to be capable of generating 
ozone, it was determined to employ a number of specimens 
belonging to the genus Pelargonium not in bloom, with a view of 
ascertaining whether the reactions obtained with flowering gera- 
niums were due to the presence of the flowers, or whether they 
were due in part to the odorous principles emitted from the 
leaves of the plants. To our astonishment slight reactions were 
obtained, as shown by the eae record of results: 
No. experiment.| Schoenbein, | Guaiacum. Peo (ha Time. pom ci 
Bh bs 5 very slight | slight marked | negative tohours) clear 
Lt T a be negative negative n " A na ie 
M eee s & “ io à “ 
No hn ics "e negative “ Wen rainy 
E Fs. seus very ‘slight „very slight be c lo“ | clear 
Woe Vie e ss 5 negative slight « " goe i 
No. vil....:...| very slight i marked had 9 “ jpa’ly clou’y 
BM VES. css 0 negative | negative | negative e * rainy 
NOIX Perera si marked marked spe oo clear 
os a ENS marked slight slight > oo — 
Ma REA. aa slight = negative é 9 * cloudy 
a C negative ' negative ve r= rainy 
Although there were but three “ very slight” reactions, one 
“slight ” and one “marked” with the Schoenbein obtained in the: 
twelve experiments here recorded; this is not a bad showing 
when it is recollected that four of the tests giving no indication 
of ozone were made on rainy days, it having been shown in the 
former investigations that sunlight or at least good diffused light 
is an essential condition to the generation of ozone by plants. 
Upon this point, however, the evidence afforded by the results 
of the present set of experiments alone is too slender on which 
to base positive conclusions, and hence we deemed it desirable to 
make further observations upon foliage possessed with marked 
perfume. To aid in clearing up this subject it was next resolved 
to make tests with pine foliage, possessing the well-known tere- 
binthinate odor, and in the results obtained we were not dis- 
appointed, 
Seven branches taken from the species Pious strobus were 
introduced into the case in the upright — when the same 
