Car. II, THE PROCESS OF AGGREGATION. 43 
now all their cells had undergone aggregation; so had the cells 
of the exterior tentacles which had become inflected through 
the irritation transmitted from the glands of the disc, on which 
the transported particles rested. This was likewise the case with 
the short tentacles round the margins of the disc, which had not 
as yet become inflected. This latter fact shows that the pro- 
cess of aggregation is independent of the inflection of the ten- 
tacles, of which indeed we have other and abundant evidence. 
Again, the exterior tentacles on three leaves were carefully 
examined, and found to contain only homogeneous purple fluid; 
little bits of thread were then placed on the glands of three of 
them, and after 22 hrs. the purple fluid in their cells almost 
down to their bases was aggregated into innumerable, spherical, 
elongated, or filamentous masses of protoplasm. The bits of 
thread had been carried some time previously to the central 
disc, and this had caused all the other tentacles to become 
somewhat inflected; and their cells had likewise undergone 
aggregation, which however, it should be observed, had not 
as yet extended down to their bases, but was confined to the 
cells close beneath the glands. 
Not only do repeated touches on the glands* and the contact 
of minute particles cause aggregation, but if glands, without 
being themselves injured, are cut off from the summits of the 
pedicels, this induces a moderate amount of aggregation in the 
headless tentacles, after they have become inflected. On the 
other hand, if glands are suddenly crushed between pincers, as 
was tried in six cases, the tentacles seem paralysed by so great 
a shock, for they neither become inflected nor exhibit any signs 
of aggregation. 
Carbonate of Ammonia.—Of all the causes inducing aggrega- 
tion, that which, as far as I have seen, acts the quickest, and is 
the most powerful, is a solution of carbonate of ammonia. What- 
ever its strength may be, the glands are always affected first, 
and soon become quite opaque,so as to appear black. For 
instance, I placed a leaf in a few drops of a strong solution, 
namely, of one part to 146 of water (or 3 grs. to 1 oz.), and 
observed it under a high power. All the glands began to 
* Judging from an account of 
M. Heckel’s observations, which 
I have only just seen quoted in 
the ‘ Gardener’s Chronicle’ (Oct. 
19, 1874), he appears to have 
observed a similar phenomenon in 
the stamens of Berberis, after 
they have been excited by a 
touch and have moved; for he 
says, ‘the contents of each indi- 
vidual cell are collected together 
in the centre of the cavity.” 
