196 DROSERA ROTUNDIFOLIA. CHAP. VUL 



an immersion of 8 hrs. 20 m. the leaves were washed and placed 

 in water; next morning, after about 16 hrs., they were still 

 inflected and discoloured ; on the succeeding day they were 

 evidently dead. Two leaves were immersed in a stronger 

 mixture, of one part to fifty of water ; in 1 hr. 15 m. the glands 

 became as white as porcelain, as if they had been dipped in boil- 

 ing water ; very few of the tentacles were inflected ; but after 

 4 hrs. almost all were inflected. These leaves were then placed 

 in water, and next morning were evidently dead. Half-minim 

 drops of the same strength (viz. one part to fifty of water) were 

 next placed on the discs of five leaves ; after 21 hrs. all the 

 outer tentacles were inflected, and the leaves appeared much 

 injured. I likewise touched the secretion round a large number 

 of glands with minute drops (about ^ of a minim, or '00296 ml.) 

 of Scheele's mixture (6 percent.); the glands first became bright 

 red, and after 3 hrs. 15 m. about two-thirds of the tentacles 

 bearing these glands were inflected, and remained so for the two 

 succeeding days, when they appeared dead. 



Concluding Remarks on the Action of Acids. It is 

 evident that acids have a strong tendency to cause the 

 inflection of the tentacles ; * for out of the twenty-four 

 acids tried, nineteen thus acted, either rapidly and 

 energetically, or slowly and slightly. This fact is 

 remarkable, as the juices of many plants contain more 

 acid, judging by the taste, than the solutions employed 

 in my experiments. From the powerful effects of so 

 many acids on Drosera, we are led to infer that those 

 naturally contained in the tissues of this plant, as well 

 as of others, must play some important part in their 

 economy. Of the five cases in which acids did not 

 cause the tentacles to be inflected, one is doubtful ; 

 for uric acid did act slightly, and caused a copious 

 secretion of mucus. Mere sourness to the taste is no 



"According to M. Fournier Berberis instantly to close; though 



(' De la Fecondation dims les drops of water have no siich power, 



Phanerogames." 18(53, p. 61) drops which latter statement I can cour 



of acetic, hydrocyanic, and sul- firm, 

 phtiric acid cave the stamens of 



