78 DUOSERA HOTUNDIFOLIA. CHAP. V 



30 lirs. Inflection was never thus caused. It is necessary 

 to try pure gum arabic, for a friend tried a solution bought 

 ready prepared, and this caused the tentacles to bend ; but he 

 afterwards ascertained that it contained much animal matter, 

 probably glue. 



Sugar. Drops of a solution of white sugar of three strengths 

 (the weakest containing one part of sugar to 73 of water) were 

 left on fourteen leaves from 32 hrs. to 48 lirs. ; btit no effect was 

 produced. 



Starch. A mixture about as thick as cream was dropped on 

 six leaves and left on them for 30 hrs., no effect being produced. 

 I am surprised at this fact, as I believe that the starch of com- 

 merce generally contains a trace of gluten, and this nitrogenous 

 substance causes inflection, as we shall see in the next chapter. 



Alcohol, Diluted. One part of alcohol was added to seven of 

 water, and the usual drops were placed on the discs of three 

 leaves. No inflection ensued in the course of 48 hrs. To ascer- 

 tain whether these leaves had been at all injured, bits of meat 

 were placed on them, and after 24 hrs. they were closely inflected. 

 I also put drops of sherry -wine on three other leaves ; no inflec- 

 tion was caused, though two of them seemed somewhat injured. 

 We shall hereafter see that cut-off leaves immersed in diluted 

 alcohol of the above strength do not become inflected. 



Olive Oil. Drops were placed on the discs of eleven leaves, and 

 no effect was produced in from 24 hrs. to 48 hrs. 'Four of these 

 leaves were then tested by bits of meat on their discs, and three 

 of them were found after 24 hrs. with all their tentacles and 

 blades closely inflected, whilst the fourth had only a few ten- 

 tacles inflected. It will, however, be shown in a future place, 

 that cut-off leaves immersed in olive oil are powerfully affected. 



Jnfusion and Decoction of Tm. Drops of a strong infusion and 

 decoction, as well as of a rather weak decoction, of tea were 

 placed on ten leaves, none of which became inflected. I after- 

 wards tested three of them by adding bits of meat to the drops 

 which still remained on their discs, and when I examined them 

 after 24 hrs. they were closely inflected. The chemical principle 

 of tea, namely theine, was subsequently tried and produced no 

 effect. The albuminous matter which the leaves must originally 

 have contained, no doubt, had been rendered insoluble by their 

 having been completely dried. 



We thus see that, excluding the experiments with 

 water, sixty-one leaves were tried with drops of the 



