Ouap. VII. NITRATE OF AMMONIA. 149 
7 hrs., but the full effect was not produced until from 24 hrs. tc 
30 hrs. had elapsed. Two of the leaves, which were only slightly 
inflected, re-expanded after an additional interval of 19 hrs. 
Half-minims of a rather weaker solution, viz. of one part tc 
_ 1812 of water (1 gr. to 3 oz.) were tried on fourteen leaves ; so that 
each received zg, of a grain (0225 mg.), instead of, as in the last 
experiment, g255 Of a grain. The blade of one was plainly in- 
flected, as were six of the exterior tentacles; the blade of a second 
was slightly, and two of the exterior tentacles well, inflected, all 
the other tentacles being curled in at right angles to the disc; 
three other leaves had from five to eight tentacles inflected; five 
others only two or three, and occasionally, though very rarely, 
drops of pure water cause this much action; the four remaining 
leaves were in no way affected, yet three of them, when subse- 
quently tried with urine, became greatly inflected. In most of 
these cases a slight effect was perceptible in from 6 hrs. to 
7 brs., but the full effect was not produced until from 24 hrs, 
to 30 hrs. had elapsed. It is obvious that we have here reached 
very nearly the minimum amount, which, distributed between 
the glands of the disc, acts on the exterior tentacles; these 
having themselves not received any of the solution. 
In the next place, the viscid secretion round three of the 
exterior glands was touched with the same little drop (5 of a 
minim) of a solution of one part to 437 of water; and after an 
interval of 2 hrs. 50 m. all three tentacles were well inflected. 
Each of these glands could have received only the ggig5 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 dises, that the nitrate 
of ammonia is more potent in causing inflection than the car- 
bonate ; for minute drops of the latter salt of this strength pro- 
duced 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. 
