154 DROSERA ROTUNDIFOLIA. Ouap. VIL 
given, which are so surprising that their credi- 
bility requires every kind of support. In 1872 I 
experimented on twelve immersed leaves, giving each 
only ten minims of a solution; but this was a bad 
method, for so small a quantity hardly covered them. 
None of these experiments will, therefore, be given, 
though they indicate that excessively minute doses 
are efficient. When I read over my notes, in 1873, 
I entirely disbelieved them, and determined to make 
another set of experiments with scrupulous care, on 
the same plan as those made with the nitrate; namely 
by placing leaves in watch-glasses, and pouring over 
each thirty minims of the solution under trial, treat- 
ing at the same time and in the same manner other 
leaves with the distilled water used in making the 
solutions. During 1873, seventy-one leaves were thus 
tried in solutions of various strengths, and the same 
number in water. Notwithstanding the care taken 
and the number of the trials made, when in the 
following year I looked merely at the results, without 
reading over my observations, I again thought that 
there must have been some error, and thirty-five fresh 
trials were made with the weakest solution; but 
the results were as plainly marked as before. Al- 
together, 106 carefully selected leaves. were tried, 
both in water and in solutions of the phosphate. 
Hence, after the most anxious consideration, I can 
entertain no doubt of the substantial accuracy of my 
results. 
Before giving my experiments, it may be well to premise that 
crystallised phosphate of ammonia, such as I used, contains 
35°33 per cent. of water of crystallisation; so that in all the 
following trials the efficient elements formed only 64°67 per 
cent. of the salt used. 
Extremely minute particles of the dry phosphate were placed 
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