8 
New Phase of Plant-Life . 
[January, 
inflexion of the tentacles ; but the case is very different 
with fluids containing nitrogen, whether in the shape of 
organic compounds or of ammoniacal salts. Nine salts of 
ammonia which were applied to the plant, in the state of 
weak solution, all caused the inflexion of the tentacles, and 
frequently also of the blade of the leaf. Of all the salts 
tried the phosphate is by far the most powerful stimulant. 
The i-gSqoth part of a grain placed on the glands of the 
disc, so as to a Ct indirectly upon the outer tentacles, pro- 
duced this result. But this is far from being the limit. If 
the solution was applied for a few seconds direCtly to the 
gland of an outer tentacle, 1-153, booth of a grain was 
sufficient, whilst if the leaf was entirely immersed — allowing 
time for every gland to absorb all that it can— inflection was 
produced by the almost inconceivably small quantity of 
1-19,760, oooth of a grain. As, moreover, the phosphate of 
ammonia in question contains 35 per cent of crystalline 
water, the really efficient aCtive matter in the solution 
would be, in round numbers, the 1-30, 000, oooth of a grain ! 
This is a degree of sensitiveness far surpassing that of any 
method of analysis, with the exception of the spectroscope. 
Dissolve 1 grain of phosphate of ammonia in a 31-gallon 
cask full of water. Of this solution take J a drachm. The 
most sensitive reagents, in the hands of the most skilful 
chemist, will fail to show the presence of the salt. Yet the 
Drosera — a plant without any specialised nervous system, 
insensient in common belief as the clods of the valley — 
detects it at once. We see no reason here for suspecting 
any error. The salt, Mr. Darwin informs us, “ was in some 
cases weighed for me by a chemist in an excellent balance.’’ 
Now it is scarcely necessary to observe that balances of 
modern construction, and chemists of modern training, are 
required to weigh with accuracy much smaller amounts than 
1 grain. The quantities of water in which this i-grain 
dose was to be dissolved were many times measured with 
great care. The experiments were repeated during several 
years by Mr. Darwin himself and his two sons, who were at 
first as incredulous as himself ; and simultaneous trials 
were made with other leaves, immersed in still weaker 
solutions and in pure water, by way of control. “ I hope,” 
adds the distinguished author, “ that some one may here- 
after be induced to repeat my experiments : in this case he 
should seleCt young and vigorous leaves, with the glands 
surrounded by abundant secretion. The leaves should be 
carefully cut off and laid gently in watch-glasses, and a 
measured quantity of the solution and of water poured over 
