192 DROSERA ROTUNDIFOLIA Cuar. VIII 
evidently dead. This acid is far more powerful than formic, and 
is highly poisonous. Half-minim drops of a stronger mixture 
(viz. oné 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 ull died after two days. 
Propionic Acid.—Three leaves were immersed in ninety minims 
of a mixture of one part to 487 of water; in 1 hr. 50 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 morning, after 20 hrs., most of the glands were 
very paie, 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 slightly 
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 Giycerine and Oleic Acid in Watts’ ‘Dict. af 
Chemistry.’ 
