122 DROSERA ROTUNDIFOLIA. [Cuar. VII. 
could have received only the usivo Of a grain, or *00225 mg. A 
little drop of the same size and strength was also applied to four other 
glands, and in 1 hr. two became inflected, whilst the other two never 
moved. We here see, as in the case of the half-minims placed on 
the discs, that the nitrate of ammonia is more potent in causing 
inflection than the carbonate; for minute drops of the latter salt 
of this strength produced no effect. I tried minute drops of a still 
weaker solution of the nitrate, viz. one part to 875 of water, on 
twenty-one glands, but no effect whatever was produced, except 
perhaps in one instance. 
Sixty-three leaves were immersed in solutions of various strengths; 
other leaves being immersed at the same time in the same pure water 
used in making the solutions. The results are so remarkable, though 
less so than with phosphate of ammonia, that I must describe the 
experiments in detail, but I will give only a few. In speaking of the 
successive periods when inflection occurred, I always reckon from the 
time of first immersion, 
Having made some preliminary trials as a guide, five leaves were 
placed in the same little vessel in thirty minims of a solution of one 
part of the nitrate to 7875 of water (1 gr. to 18 oz.); and this amount 
of fluid just sufficed to cover them. After 2 hrs. 10 m. three of the 
leaves were considerably inflected, and the other two moderately. The 
glands of all became of so dark a red as a’most to deserve to be called 
black. After 8 hrs. four of the leaves had all their tentacles more or 
less inflected ; whilst the fifth, which I then perceived to be an old 
leaf, had only thirty tentacles inflected. Next morning, after 23 hrs. 
40 m., all the leaves were in the same state, excepting that the old 
leaf had a few more tentacles inflected. Five leaves which had been 
placed at the same time in water were observed at the same intervals 
of time; after 2 hrs. 10 m. two of them had four, one had seven, one 
had ten, of the long-headed marginal tentacles, and the fifth had four 
round-headed tentacles, inflected. After 8 hrs. there was no change 
in these leaves, and alter 24 hrs. all the marginal tentacles had re- 
expanded ; but in one leaf,-a dozen, and in a second leaf, half a dozen, 
submarginal tentacles had become inflected. As the glands of the 
five leaves in the solution were simultaneously darkened, no doubt 
they had all absorbed a nearly equal amount of the salt: and as yt 
of a grain was given to the five leaves together, each got zg of a 
grain (-045 mg.). I did not count the tentacles on these leaves, which 
were moderately fine ones, but as the average number on thirty-one 
leaves was 192, it would be safe to assume that each bore on an average 
at least 160. If so, each of the darkened glands could have received 
only sydzgz Of a grain of the nitrate ; and this caused the inflection of 
a great majority of the tentacles. 
This plan of immersing several leaves in the same vessel is a bad 
cne, as it is impossible to feel sure that the more vigorous leaves do 
not rob the weaker ones of their share of the salt. The glands, more- 
over, must often touch one another or the sides of the vessel, and 
