160 DROSERA ROTUNDIFOLIA. [Chap. VIIL 



3 hrs. 45 m. all strongly inflected, and the surrounding fluid col- 

 oureti pink; after 6 hrs. all closely inflected. After an iiiunersion 

 of 8 hrs. 20 ni. the leaves were washed and placed in water; next 

 morning, after about 10 hrs., they were still inflected and discol- 

 oured; 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 boiling 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 ap- 

 peared much injured. I likewise touched the secretion round a 

 large number of glands with minute drops (about -^ of a minim, or 

 .00296 c.c.) of Scheele's mixture (containing 4 per cent, of anhy- 

 drous acid) ; 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 evi- 

 dent that acids have a strong tendency to cause the inflection 

 of the tentacles;* for, out of twenty-four acids tried, nine- 

 teen 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 econ- 

 omy. 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 criterion of the power of an acid 

 on Drosera, as citric and tartaric acids are very sour, yet do 

 not excite inflection. It is remarkable how acids differ in 

 their power. Thus, hydrochloric acid acts far less power- 

 fully than hydriodic and many other acids of the same 

 strenf^h, and is not poisonous. This is an interesting fact, 

 as hydrochloric acid plays so important a part in the diges- 



Aocordlnjr to M. Fonrnler Berbprls Instnntly to close; 



i' De la FCcondntlon dnns les though drops of water have no 



>han(^roKanie8,' 18(Vi, p. 01) drops such power, which latter state- 



of acetic, hydrocyanic, and sul- ment I can confirm, 

 pburic acid cause the stamens of 



