152° DROSERA ROTUNDIFOLIA. Cuav. VIL 
in water, only one had any of its éxterior tentacles, namely five, | 
-inflected; after 6 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 48,750 of water (1 gr. to 100 oz.), so that each leaf 
got sds of a grain (0405 mg.). Of these, one was much in-- 
flected 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 
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 had all its ten- 
tacles except three inflected in 10 m., each gland (assuming that 
the leaf bore 160 tentacles) could have absorbed only zszsoq of 
a grain, or ‘000258 mg. 
Four leaves were separately immersed as before in « solution 
of one part to 131,250 of water (1 gr. to 300 0z.), so that each 
received 2,5 of a grain, or 0185 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 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 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 
jeaves 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 ggzyqq of a 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 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 ;,;5 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 
