CiiAP. VII. NITKATE OF AMMONIA. 149 



7 lirs., but the full eifect was not produced until from 24 brs. to 

 30 lirs. 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 to 

 1312 of water (1 gr. to 3 oz.) were tried on fourteen leaves ; so that 

 each received -gsVo o^ ^ grain (-0225 mg.), instead of, as in the last 

 experiment, a^Vo ^^ ^ 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 afiected, 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 hrs., 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 (J^ 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 -gs^oo ^^ ^ 

 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 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. 



