Pane Pe ee 
Car. IIL.] THE PROCESS OF AGGREGATION. 45 
the tentacles were not inflected. Glycerine causes in a few minutes 
well-pronounced aggregation, commencing as usual within the glands 
and then travelling down the tentacles; and this I presume may be 
attributed to the strong attraction of this substance for water. 
Immersion for several hours in water causes some degree of aggrega- 
tion. Twenty leaves were first carefully examined, and re-examined 
after having been left immersed in distilled water for various periods, 
with the following results. It is rare to find even a trace of aggrega- 
tion until 4 or 5 and generally not until several more hours have 
elapsed. When, however, a leaf becomes quickly inflected in water, as 
sometimes happens, especially during very warm weather, aggregation 
may occur in little over 1 hr. In all cases leaves left in water for 
more than 24 hrs. have their glands blackened, which shows that 
their contents are aggregated; and in the specimens, which were 
carefully examined, there was fairly well-marked aggregation in the 
upper cells of the pedicels. These trials were made with cut-off leaves, 
and it occurred to me that this circumstance might influence the 
result, as the footstalks would not perhaps absorb water quickly 
enough to supply the glands as they continued to secrete. But this 
view was proved erroneous, for a plant with uninjured roots, bearing 
four leaves, was submerged in distilled water for 47 hrs., and the 
glands were blackened, though the tentacles were very little inflected. 
In one of these leaves there was only a slight degree of aggregation in 
the tentacles; in the second rather more, the purple contents of the 
cells being a little separated from the walls; in the third and fourth, 
which were pale leaves, the aggregation in the upper parts of the 
pedicels was well marked. In these leaves the little masses of proto- 
plasm, many of which were oval, slowly changed their forms and 
positions; so that a submergence for 47 hrs. had not killed the proto- 
plasm. In a previous trial with a submerged plant the tentacles were 
not in the least inflected. 
Heat induces aggregation. A leaf, with the cells of the tentacles 
containing only homogeneous fluid, was waved about for 1 m. in water 
at 130° Fahr. (54°°4 Cent.), and was then examined under the micro- 
scope as quickly as possible, that is in 2 m. or 3 m.; and by this time 
the contents of the cells had undergone some degree of aggregation. 
A second leaf was waved for 2 m. in water at 125° (51°°6 Cent.) and 
quickly examined as before; the tentacles were well inflected; the 
purple fluid in all the cells had shrunk a little from the walls, and 
contained many oval and elongated masses of protoplasm, with a few 
minute spheres. A third leaf was left in water at 125°, until it cooled, 
and, when examined after 1 hr. 45 m., the inflected tentacles showed 
some aggregation, which became after 3 hrs. more strongly marked, 
but did not subsequently increase. Lastly, a leaf was waved for 1 m, 
in water at 120° (48°°8 Cent.) and then left for 1 hr. 26 m. in cold 
water; the tentacles were but little inflected, and there was only 
here and there a trace of aggregation. In all these and other trials 
with warm water the protoplasm showed much less tendency to 
