The process of aggregation is a vital one; by which I mean that the contents of the cells must be alive and uninjured to be thus affected, and they must be in an oxygenated condition for the transmission of the process at the proper rate.  Some tentacles in a drop of water were strongly pressed beneath a slip of glass; many of the cells were ruptured, and pulpy matter of a purple colour, with granules of all sizes and shapes, exuded, but hardly any of the cells were completely emptied.  I then added a minute drop of a solution of one part of carbonate of ammonia to 109 of water, and after 1 hr. examined the specimens.  Here and there a few cells, both in the glands and in the pedicels, had escaped being ruptured, and their contents were well aggregated into spheres which were constantly changing their forms and positions, and a current could still be seen flowing along the walls; so that the protoplasm was alive.  On the other hand, the exuded matter, which was now almost colourless instead of being purple, did not exhibit a trace of aggregation.  Nor was there a trace in the many cells which were ruptured, but which had not been completely emptied of their contents.  Though I looked carefully, no signs of a current could be seen within these ruptured cells.  They had evidently been killed by the pressure; and the matter which they [page 58] still contained did not undergo aggregation any more than that which had exuded.  In these specimens, as I may add, the individuality of the life of each cell was well illustrated.

A full account will be given in the next chapter of the effects of heat on the leaves, and I need here only state that leaves immersed for a short time in water at a temperature of 120oFahr. (48o.8 Cent.), which, as we have seen, does not immediately induce aggregation, were then placed in a few drops of a strong solution of one part of carbonate of ammonia to 109 of water, and became finely aggregated.  On the other hand, leaves, after an immersion in water at 150o (65o.5 Cent.), on being placed in the same strong solution, did not undergo aggregation, the cells becoming filled with brownish, pulpy, or muddy matter.  With leaves subjected to temperatures between these two extremes of 120o and 150o Fahr. (48o.8 and 65o.5 Cent.), there were gradations in the completeness of the process; the former temperature not preventing aggregation from the subsequent action of carbonate of ammonia, the latter quite stopping it.  Thus, leaves immersed in water, heated to 130o (54o.4 Cent.), and then in the solution, formed perfectly defined spheres, but these were decidedly smaller than in ordinary cases.  With other leaves heated to 140o (60o Cent.), the spheres were extremely small, yet well defined, but many of the cells contained, in addition, some brownish pulpy matter.  In two cases of leaves heated to 145o (62o.7 Cent.), a few tentacles could be found with some of their cells containing a few minute spheres; whilst the other cells and other whole tentacles included only the brownish, disintegrated or pulpy matter.