20 DROSERA ROTUNDIFOLIA. (Cuar. IL. 
repeatedly proved by trials with bits of meat ; but Iwill here 
give only the case of a minute fly, naturally caught and still 
alive, which I found adhering by its delicate feet to the 
glands on the extreme left side of the central disc. The 
marginal tentacles on this side closed inwards and killed the 
fly, and after a time the edge of the leaf on this side also 
became inflected, and thus remained for several days, whilst 
neither the tentacles nor the edge on the opposite side were 
in the least affected. 
If young and active leaves are selected, inorganic particles 
not larger than the head of a small pin, placed on the central 
glands, sometimes cause the outer tentacles to bend inwards. 
But this follows much more surely and quickly, if the object 
contains nitrogenous matter which can be dissolved by the 
secretion. On one occasion I observed the following unusual 
circumstance. Small bits of raw meat (which acts more 
energetically than any other substance), of paper, dried moss, 
and of the quill of a pen were placed on several leaves, and 
they were all embraced equally well in about 2 hrs. On 
other occasions the above-named substances, or more commonly 
particles of glass, coal-cinder (taken from the fire), stone, 
gold-leaf, dried grass, cork, blotting-paper, cotton-wool, and 
hair rolled up into little balls, were used, and these substances, 
though they were sometimes well embraced, often caused no 
movement whatever in the outer tentacles, or an extremely 
slight and slow movement. Yet these same leaves were 
proved to be in an active condition, as they were excited to 
move by substances yielding soluble nitrogenous matter, such 
as bits of raw or roast meat, the yolk or white of boiled eggs, 
fragments of insects of all orders, spiders, &c. I will give 
only two instances. Minute flies were placed on the discs of 
several leaves, and on others balls of paper, bits of moss and 
quill of about the same size as the flies, and the latter were 
well embraced in a few hours; whereas after 25 hrs. only a 
very few tentacles were inflected over the other objects. 
The bits of paper, moss, and quill were then removed from 
these leaves, and bits of raw meat placed on them; and now 
all the tentacles were soon energetically inflected. 
Again, particles of coal cinder (weighing rather more than 
the flies used in the last experiment) were placed on the 
centres of three leaves: after an interval of 19 hrs. one of the 
particles was tolerably well embraced; a second by a very 
tew tentacles; and a third by none. I then removed the 
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