218 KECENT RESEARCHES ON THE RESPIRATION OF PLANTS. 



Experiments to shoiv that the carbonic acid exhaled in a limited 

 atmosphere is reduced in the day time as it is (jiven out by the 

 plant. 



Names of Plants. 



°,3 >: 



•5 2 



Observations. 



2 \Kitaibelia vitifolia 

 A Rhus radicaiis , ' 

 _ \Fra.Tiiiu$ excelsior 

 _ >-4ce;' eriocarpon • 



ASyringa vulgaris. 



1 )Gli/ci/rrJnza eckiA 

 2) nata . . ./ 



AAsclepii 



1 \Fagopyrum 

 2) viosum . 



lets cornuti 



cus carica. 



SOJuly 

 3lJuly 



1 Aug. 



1 Aug. 



4 Aug. 

 7 Aug. 



5 Aug. 



6 Aug. 

 6 Aug. 



•without) 



with J 

 without I 



with J 

 without] 



with 

 without 1 



with 

 without) 



with 

 without! 



with 

 without) 



with 

 without) 



with 

 without) 



with J 



hours. 



10 to 4 



11 to .5 



11 to 5 



12 to 6 

 12 to 6 

 12 to 6 



7 to 7 

 7 to 7 

 9 to 6 



[Si 



{u} 



{l\ 



WW 

 K) 

 [l] 

 [^ 



Showery weather with 

 afewrays of sunshine. 



Damp and rather dull 

 Aveather. 



No sun, rather dull, 

 rain. 



Rather dull. 



Three hours of bright 

 sunshine. 



Four hours of sun. 



Exposed to a bright sud 

 during 6 hours. 



Ditto. 

 Ditto. 



These experiments, made with the greatest care, sliow to 

 demonstration that not only the carbonic acid exhaled whilst the 

 plant is exposed to the sun is to a great extent reduced under 

 its influence as the gas is given off, but that this also takes place 

 in the shade even on a cloudy day : this may explain the oc- 

 casional rapid growth of plants during a long succession of dull 

 rainy days in the climate of Lille. The above experiments were 

 made in the apparatus already described, and in the examples num- 

 bered 1 the quantity of gas was ascertained by means of baryta- 

 water introduced through the safety tube as soon as the experiment 

 was over. It is scarcely necessary to remark that in the examples 

 numbered 2, the whole of the gas given off is not represented, 

 some of it having been reduced by the leaves, the surface of 

 which was much larger than that of the baryta-water at the 

 bottom of the vase. It must also be observed that, as is shown in 

 the following table, experiments made in the sun, and in a high 

 temperature, give a larger amount of carbonic acid. 



