Chap. VII. NITRATE OF AMMONIA. 151 



5 hrs. 30 m. two leaves had all their tentacles inflected; a 

 third leaf all except the extreme marginals, which seemed old 

 and torpid ; and the fourth a large number. After 21 hrs. 

 every single tentacle, on all four leaves, was closely inflected. 

 Of the four leaves placed at the same time in water, one had, 

 after 5 hrs. 45 m., five marginal tentacles inflected ; a second, 

 ten ; a third, nine marginals and submarginals ; and the fourth, 

 twelve, chiefly submarginals, inflected. After 21 hrs. all these 

 marginal tentacles re-expanded, but a few of the submarginals 

 on two of the leaves remained slightly curved inwards. The 

 contrast was wonderfully great between these four leaves in 

 water and those in the solution, the latter having every one of 

 their tentacles closely inflected. Making the moderate assump- 

 tion that each of these leaves bore 160 tentacles, each gland 

 could have absorbed only ^ g ^^3 ^ ^ of a grain (-000351 mg.). 

 This experiment was repeated on three leaves with the same 

 relative amount of the solution ; and after 6 hrs. 15 m. all the 

 tentacles except nine, on all three leaves taken, together, were 

 closely inflected. In this case the tentacles on each leaf were 

 counted, and gave an average of 162 per leaf. 



The following experiments were tried during the summer of 

 1873, by placing the leaves, each in a separate watch-glass and 

 pouring over it thirty minims (1775 ml.) of the solution; other 

 leaves being treated in exactly the same manner with the 

 doubly distilled water used in making the solutions. The 

 trials above given were made several years before, and when I 

 read over my notes, I could not beheve in the results; so I 

 resolved to begin again with moderately strong solutions. Six 

 leaves were first immersed, each in thirty minims of a solution of 

 one part of the nitrate to 8750 of water (1 gr. to 20 oz.), so that 

 each received -^ of a grain (2025 mg.). Before 30 m. had 

 elapsed, four of these leaves were immensely, and two of them 

 nfoderately, inflected. The glands were rendered of a dark 

 red. The four corresponding leaves in water were not at all 

 affected until 6 hrs. had elapsed, and then only the short ten- 

 tacles on the borders of the disc; and their inflection, as 

 previously explained, is never of any significance. 



Four leaves were immersed, each in thirty minims of a solu- 

 tion of one part to 17,500 of water (1 gr. to 40 oz.), so that each 

 received qIq of a grain (lOl mg.); and in less than 45 m. three 

 of them had all their tentacles, except from four to ten, inflected ; 

 the blade of one being inflected after 6 hi's., and the blade of a 

 second after 21 hrs. The fourth leaf was not at all affected. 

 The glands of none were darkened. Of the corresponding leaves 



