Caar. VILJ PHOSPHATE OF AMMONIA. 129 
Twenty leaves were immersed in the usual manner, each in thirty 
minims of a solution of one part to 218,750 of water (1 gr. to 500 oz.). 
So many leaves were tried because I was then under the false im- 
pression that it was incredible that any weaker solution could produce 
an effect. Each leaf received ggg of a grain, or 0081 mg. ‘The first 
eight leaves which I tried both in the solution and water were either 
young and pale or too old; and the weather was not hot. They were 
hardly at all affected; nevertheless, it would be unfair to exclude 
them. I then waited until I had got eight pairs of fine leaves, and the 
weather was favourable, the temperature of the room where the leaves 
were immersed varying from 75° to 81° (23°8 to 27%2Cent.). In 
another trial with four pairs (included in the above twenty pairs), the 
temperature in my room was rather low, about 60° (15°°5 Cent.); but 
the plants had been kept for several days in a very warm greenhouse 
and thus rendered extremely sensitive. Special precautions were 
taken for this set of experiments; a chemist weighed for me a grain in 
an excellent balance; and fresh water, given me by Professor Frank- 
land, was carefully measured. The leaves were selected from a large 
number of plants in the following manuer: the four finest were 
immersed in water, and the next four finest in the solution, and so on 
till the twenty pairs were complete. The water specimens were thus a 
little favoured, but they did not undergo more inflection than in the 
previous cases, comparatively with those in the solution. 
Of the twenty leaves in the solution, eleven became inflected witbin 
40 m.; eight of them plainly aud three rather doubtfully; but the 
latter had at least twenty of their outer tentacles inflected. Owing to 
the weakness of the solution, inflection occurred, except in No. 1, 
much more slowly than in the previous trials. ‘lhe condition of the 
eleven leaves which were considerably inflected will now be given at 
stated intervals, always reckoning from the time of immersion :— 
(1) After only 8 m. a large number of tentacles inflected, and after 
17 m. all but fifteen; after 2 hrs. all but eight inflected, or plainly 
sub-inflected. After 4 hrs. the tentacles began 1o re-expand, and such 
prompt re-expansion is unusual; after 7 hrs. 80 m. they were almost 
fully re-expanded. 
(2) After 39 m. a large number of tentacles inflected; after 2 hrs, 
18 m. all but twenty-five inflected; after 4 hrs. 17 m. all but sixteen 
inflected. The leaf remained in this state for many hours. 
(3) After 12 m. a considerable amount of inflection: after 4 hrs. all 
the tentacles inflected except those of the two outer rows, and the leaf 
remained in this state for some time; after 23 hrs. began to re-expand. 
(4) After 40 m. much inflection; after 4 hrs. 13 m. fully half the 
tentacles inflected; after 23 hrs. still slightly inflected. 
(5) After 40 m. much inflection; after 4 hrs. 22 m. fully half the 
tentacles inflected ; after 23 hrs. still slightly inflected. 
(6) After 40 m. some inflection; after 2 hrs. 18 m. about twenty- 
eight outer tentacles inflected; after 5 hrs. 20 m. about a third of the 
tentacles inflected ; after 8 hrs. much re-expanded. 
K 
