192 DKOSERA EOTUNDIFOLIA. CnAr. VIIL 



evidently dead. This acid is far more powerful than formic, and 

 is highly poisonous. Half-minim drops of a stronger mixture 

 (viz. one part by measure to 320 of water) were placed on the 

 discs of five leaves ; none of the exterior tentacles, only those 

 on the borders of the disc which actually absorbed the acid, 

 became inflected. Probably the dose was too strong and para- 

 lysed the leaves, for drops of a weaker mixture caused much 

 inflection ; nevertheless the leaves all died after two days. 



Propionic Acid. — Three leaves were immersed in ninety minims 

 of a mixture of one part to 437 of water ; in 1 hr. 60 m. there 

 was no inflection ; but after 3 hrs. 40 m. one leaf was greatly 

 inflected, and the other two slightly. The inflection continued 

 to increase, so that in 8 hrs. all three leaves were closely in- 

 flected. Next mormng, after 20 hrs., most of the glands were 

 very pale, but some few were almost black. No mucus had been 

 secreted, and the surrounding fluid was only just perceptibly 

 tinted of a pale pink. After 46 hrs. the leaves became shghtly 

 flaccid and were evidently killed, as was afterwards proved to 

 be the case by keeping them in water. The protoplasm in the 

 closely inflected tentacles was not in the least aggregated, but 

 towards their bases it was collected in little brownish masses at 

 the bottoms of the cells. This protoplasm was dead, for on 

 leaving the leaf in a solution of carbonate of ammonia, no 

 aggregation ensued. Propionic acid is highly poisonous to 

 Drosera, like its ally acetic acid, but induces inflection at a 

 much slower rate. 



Oleic Acid (given me by Prof. Frankland). — Three leaves were 

 immersed in this acid ; some inflection was almost immediately 

 caused, which increased slightly, but then ceased, and the leaves 

 seemed killed. Next morning they were rather shrivelled, and 

 many of the glands had fallen off the tentacles. Drops of this 

 acid were placed on the discs of four leaves ; in 40 m. all the 

 tentacles were greatly inflected, excepting the extreme marginal 

 ones ; and many of these after 3 hrs. became inflected. I was 

 led to try this acid from supposing that it was present (which 

 does not seem to be the case)* in olive oil, the action of which 

 is anomalous. Thus drops of this oil placed on the disc do not 

 cause the outer tentacles to be inflected ; yet when minute 

 drops were added to the secretion surrounding the glands of the 

 outer tentacles, these were occasionally, but by means always, 

 inflected. Two leaves were also immersed in this oil, and there 



* See articles on Glycerine and Oleic Acid in Watts' 'Diet, of 

 Chemistry.' 



