190 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. lviii. 



in germination made by the seeds during an experiment. 

 The seeds experimented upon were chiefly oleaginous and 

 leguminous, with the exception of Indian corn, which was 

 the only seed which approached in composition the seeds 

 of wheat or barley. 



Dr. Pauchon concludes from his experiments : — 



1. That light accelerates in a constant manner the 



absorption of oxygen by germinating seeds in 

 all cases. 



2. That a relation exists between the degree of 



illumination and the quantity of oxygen 

 absorbed. 



3. That the respiratory acceleration, exercised by 



light, persists in obscurity for some hours. 



4. That the differences between the amounts of 



oxygen absorbed in light and in darkness are 

 more considerable at a low than at a high 

 temperature. 

 According to the experimental record, the first con- 

 clusion seems to be well established, and in that case 

 the second would follow almost as a matter of course. 

 The two last conclusions do not appear to me at all 

 clearly warranted, after a careful perusal of the experi- 

 ments. 



There are three possible sources of error in Dr. 

 Pauchon's experiments. The first consists in placing the 

 seeds on a pad of cotton saturated with water. In this 

 case some of the rootlets may come in contact with the 

 pad before others, and this would cause, by itself, a 

 considerable irregularity in germination by the stimulating 

 action of the moisture absorbed. The second source of 

 error is the irregularity in germination caused by selecting 

 seeds, for experiment, in which the radicle has not already 

 burst the seed coats. The third source of error is the 

 manner of securing similarity of temperature. The two 

 glass vessels containing the seeds, one clear and the 

 other covered with black paper, were placed side by side, 

 in the air, with a thermometer between them. It does 

 not seem to me at all certain that the thermometer 

 indicates the actual temperature of the interior of each 

 vessel, for the radiating powers of clear glass and black 



