326 TRANSACTIONS AND TROCEEDINGS OF THE [Sess. Lxiv. 



•experiments the- employment of a modification of the 

 phenolphthalein method, suggested by Klebs (7) in connec- 

 tion with certain algie, and recommended by Professor 

 Balfour (7) as a lecture experiment, was decided on. 



Tubes were prepared in the same way as those used in 

 the experiments on germination in the absence of carbon 

 dioxide, but with this difference, that they contained traces 

 of phenolphthalein, which imparted to the fluid a bright 

 rose tint. Such solutions retain their colour unaltered so 

 long as their reaction remains faintly alkaline, but so slight 

 is the degree of alkalinity due to the trace of lime always 

 present in ordinary tap water, and from which the carbon 

 dioxide has been driven off in Ijoiling, that the amount of 

 this gas absorbed from the atmosphere during the process 

 of cooling is frequently sufficient to produce complete 

 decoloration. When, however, the tubes are cooled in the 

 absence of carbon dioxide, and, after having been charged 

 with carefully washed buds, are finally sealed, any degrada- 

 tion of tint which may take place must be due to the carbon 

 dioxide given off by the buds during the process of respira- 

 tion ; and the rate of decoloration, as compared with that 

 in a control tube containing no buds, will be a measure of 

 the amount of carbon dioxide formed. 



By this means it is easy to prove that, as might be 

 expected, the buds respire to a slight extent during winter, 

 both in darkness and light, and also that the rate at which 

 this takes place is unaffected by illumination, while even in 

 summer the speed of carbon excretion is not greatly increased 

 so long as they are not exposed to the action of light, though 

 the unavoidable rise of temperature must to a certain extent 

 hasten the process. 



That, however, the increase due to this cause is at best 

 very small is shown by a comparison of two tubes, both of 

 which were protected from light, while one was incubated 

 in a thermostat at a temperature of 35° C, and the other 

 remained at the temperature of the room (about 10° C. to 

 15°C.). The experiment was continued for ten days, and 

 although decoloration took place in the warmed tube slightly 

 sooner than in the cool one, the acceleration due to even 

 HO considerable a difference of temperature was not very 

 marked. 



