318 



Progress of Foreign Science. 



the volume of flowers or leaves taken for unity. Thus the 

 number 8.5, which expresses in the table, the quantity of 

 oxygen gas destroyed by the Tropceolum majus, denotes that a 

 cubic centimetre, or a gramme weight of these flowers (deduct- 

 ing the peduncles), destroyed 8^ cubic centimetres of oxygen 

 gas, which were replaced by 8| cubic centimetres of carbonic 

 acid, in 200 cubic centimetres of air. The duration of the ex- 

 periments, or the abode of the flowers and leaves under the 

 receiver, was 24 hours. All the following results were ob- 

 tained in summer, sheltered from the direct action of the sun, 

 at a temperature between 18° and 25° cent. The quantity of 

 oxygen destroyed by the flowers, is greater in the sun than in 

 the shade ; a rise of temperature also augments this destruction. 

 He has inscribed on the table, the hour when the flowers were 

 plucked, and placed (with their stalk in a very little water) 

 under the receiver ; this period is especially important for those 

 which blow but a short time, and which expand only at a cer- 

 tain time of the day, as the hibiscus speciosus, cucurbita melo- 

 pepo, and the passiflora serratifolia. Only flowers, entirely de- 

 veloped, and in perfect vigour, were submitted to experiment ; 

 characters which are recognized particularly by the stamina. 



. The results here given indicate that in equal volume the 

 flowers usually destroy more oxygen than the leaves in obscu- 

 rity, or than the rest of the plant; for the leaves destroy much 

 more than the stems and the greater part of fruits. The differ- 



