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Show 56 DUOSERA ROTUNDIFOLIA. CHAP. III. of the tentacles, the glands secrete less freely, or quite cease to secrete, and the aggregated mass s of protoplasm are then redissolved. Mor over, w.hen l av~s are immersed in dense vegetable solutions, or In glycerine, the fluid within t~e gland-cells passes outwards ' and there is aggregation; and w. hen t.h e leaves are afterwards im1nersed in water, or In an Innocuous fluid of less specific gravity than water, the protoplasm is redissolved, and this, no doubt, is due to endosmosc. Opposed to this view, that aggregation is caused 1y the outward passage of fl. uid fro1n th c lls, are the following facts. There seems no close r lation between the degree of increased secretion and that of aggreo ·ation. Thus a particle of sugar add. d to th secretion round a gland causes a much great r increas of secretion, and much less aggregation, than docs a particle of carbonate of ammonia giv n in th sa1ne 1nanner. It does not app ar probabl that pure water would cause much exosmose, and yet aggre()'ation often follows from an i1nmersion in water f between 16 hrs. and 24 hrs., and always after fro1n 24 h rs. to 48 hrs. Still less probable is it that water at a tenlperature of from 125° to 130° Fahr. (51 o.6 to 54°·4 Cent.) should cause fluid to pass, not only fron1 th glands, but from all the cells of th tentacles down to their bases, so quickly that aggregation is induce l within 2 m. or 3 m. Another strong aro·um nt against this view is, that, after eomplete aggr gation, the spheres and oval mass s of protoplasm :float about in an abundant supply of thin colourless :fluid ; so that at least the latter stag s of the process cannot be due to the want of fluid to hold the protoplas1n in solution. There is still stronger evidence that aggregation is independ nt of secretion; for th papillre, described in the :first chapter, with which the CHAP. III. THE PROCESS OF AGGREGATION. 57 leaves are studded are not glandular, and do not secrete, yet they rapidly absorb carbonate of ammonia or an infusion of raw meat, and their contents then quickly undergo aggregation, which afterwards spreads into the cells of the surroun<ling tissues. We shall hereaft.er see that the purple fluid within the sensitive :filaments of Dioncca, which do not secrete, likewise undergoes aggregation from the action of a weak solution of carbonate of ammonia. 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; Jnany 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. 1-Iere and there a few cells, both in the glands and in the pedicels, had esca peel being ruptured, and their contents were well aggregated into spheres whieh 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 ahnost colourless instea.d 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 |