152 DROSEEA EOTUNDIFOLIA. Chap. VII. 



in water, only one bad any of its exterior tentacles, namely five, 

 inflected ; after 6 lirs. in one case, and after 21 hrs. in two other 

 cases, the short tentacles on the borders of the disc formed a 

 ring, in the usual manner. 



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

 of one part to 43,750 of water (1 gr. to 100 oz.), so that each leaf 

 got ^JL^ of a grain (-0105 mg.). Of these, one was much in- 

 flected in 8 m., and after 2 hrs. 7 m. bad all the tentacles, 

 except thirteen, inflected. The second leaf, after 10 m., had all 

 except three inflected. The third and fourth were hardly at all 

 affected, scarcely more than the corresponding leaves in water. 

 Of the latter, only one was affected, this having two tentacles 

 inflected, with those on the outer parts of the disc forming a 

 ring in the usual manner. In the leaf which bad all its ten- 

 tacles except three inflected in 10 m., each gland (assuming that 

 the leaf bore 160 tentacles) could have absorbed only asiVoo of 

 a grain, or -000258 mg. 



Four leaves were separately immersed as before in a solution 

 of one part to 131,250 of water (1 gr. to 300 oz.), so that each 

 received -^^ of a grain, or -0135 mg. After 50 m. one leaf had 

 all its tentacles except sixteen, and after 8 hrs. 20 m. all but 

 fourteen, inflected. The second leaf, after 40 m., had all but 

 twenty inflected; and after 8 hrs. 10 m. began to re- expand. 

 The third, in 8 hrs. had about half its tentacles inflected, which 

 began to re-expand after 8 hrs. 15 m. The fourth leaf, after 

 3 hrs. 7 m., had only twenty-nine tentacles more or less in- 

 flected. Thus three out of the four leaves were strongly acted 

 on. It is clear that very sensitive leaves had been accidentally 

 selected. The day moreover was hot. The four corresponding 

 leaves in water were likewise acted on rather more than is usual; 

 for after 3 hrs. one had nine tentacles, another four, and 

 another two, and the fourth none, inflected. With respect to 

 the leaf of which all the tentacles, except sixteen, were inflected 

 after 50 m., each gland (assuming that the leaf bore 160 ten- 

 tacles) could have absorbed only 6^2 oo ^^ ^ grain (-0000937 

 mg.), and this appears to be about the least quantity of the 

 nitrate which suffices to induce the inflection of a single tentacle. 



As negative results are imjDortant in confirming the foregoing 

 positive ones, eight leaves were immersed as before, each in thirty 

 minims of a solution of one part to 175,000 of water (1 gr. to 

 400 oz.), so that each received only -^ Jg^ of a grain (-0101 mg.). 

 This minute quantity produced a slight effect on only four of 

 the eight leaves. One had fifty-six tentacles inflected after 2 hrs, 

 13 m. ; a second, twenty-six inflected, or sub-inflected, after 



