124 DROSERA ROTUNDIFOLIA. ‘[Cuar. VIL. 
being inflected after 6 hrs., and the blade of a second after 21 hrs, 
The fourth leaf was not at all affected. ‘I'he glands of none were 
darkened. Of the corresponding leaves in water, only one had any of 
its exterior 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 furmed a ring, in the usual manner. 
Four leaves were immersed, each in thirty minims ofa solution of 
one part to 43,750 of water (1 gr. to 100 0z.), so that each leaf got 
aéoo Of a grain (°0405 mg.). Of these, one was much inflected in 8 m., 
and after 2 hrs. 7m. had all the tentacles, except thirteen, inflected, 
‘Lhe second leaf, alter 10 m., had all except three inflected. The third 
and fourth were hardly at ail affected, scarcely more than the cor- 
responding leaves in water. Of the latter, only oue was affected, this 
having two tentacles inflected, with those on the outer parts of the 
disc forining a ring in the usual manner. In the leaf which had all 
its tentacles except three inflected in 10 m., each gland (assuming 
that the leaf bore 160 tentacles) could have absorbed only gsyuqq of 
a grain, or “000258 me. 
Four leaves were separately immersed as before in a sclution of one 
part to 131,250 of water (1 gr. to $00 oz.), so that each received 45 
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 inflected. Thus three out of the four leaves were strongly acted 
on. Itis 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 (as- 
suming that the leaf bore 160 tentacles) could have absorbed only 
sorzos 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 gzhq of a grain (°0101 mg.). This minute quantity 
produced a slight effect on only tour of the cight leaves. One had 
tifty-six tentacles inflected after 2 hrs. 13 m.; a second, twenty-six 
inflected, or sub-inflected, after 38 m.; a third, eighteen inflected, after 
1hr.; and a fourth, ten inflected, after 85 m. The four other leaves 
were not in the least affected. 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 
