124 DROSERA ROTUNDIPOLU. [Chap. VII. 



second after 21 hre. The fourth leaf was not at all aflTected. The 

 glands of none were durkene<I. Of the corresponding leaves in 

 water, only one had any of its exterior tentacles, namely Ave, in- 

 flected; after (3 hrs. 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 T^xs of a grain (.0405 mg.). Of these, one was much in- 

 llected in 8 m., and after 2 hrs. 7 m. had 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 afTectcd, 

 scarcely more than the corresponding leaves in water. Of the lat- 

 ter, only one was afl"ected, 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 had all its tentacles except three in- 

 flected in 10 m., each gland (assuming that the leaf bore 160 ten- 

 tacles) could have absorbed only Tj-i^gTrff 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 re- 

 ceived xAff 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 in- 

 flected; and after 8 hrs. 10 m. began to re-expand. The third, in 

 3 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 inflected. 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, in- 

 flected. With respect to the leaf of which all the tentacles, except 

 sixteen, were inflected after 50 m., each gland (assuming that the 

 leaf bore 100 tentacles) could have absorbed only ^v^'fon o^ * 

 grain (.0000937 mg.), and this appears to be about the least quan- 

 tity of the nitrate which suflBces to induce the inflection of a 

 single tentacle. 



As negative results are important 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 ^Jt^ of a grain (.0101 mg.). 

 This minute quantity pro<luced a slight efToct on only four of 

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

 13 m. ; a sec-ond, twenty-six inflected, or sub-inflected, after 33 m. ; 

 a third, eighteen inflected, after 1 hr. ; and a fourth, ten inflected, 

 after 35 m. The four other leaves were not in the least afl'ected. 

 Of the eight corresponding leaves in water, one had, after 2 hrs. 

 10 m., nine tentacles, and four others from one to four long-headed 

 tentacles, inflected : the remaining three being unaflTectecl. Hence, 

 the y'i)5 of a grain given to a sensitive leaf during warm weather 



