56 DROSERA ROTUNDIFOLIA. Cuar. IL 
of the tentacles, the glands secrete less freely, or quite 
cease to secrete, and the aggregated masses of proto- 
plasm are then redissolved. Moreover, when leaves 
are immersed in dense vegetable solutions, or in 
glycerine, the fluid within the gland-cells passes out- 
-wards, and there is aggregation; and when the leaves 
are afterwards immersed in water, or in an innocuous 
fluid of less specific gravity than water, the protoplasm 
is redissolved, and this, no doubt, is due to endosmose. 
Opposed to this view, that aggregation is caused by 
the outward passage of fluid from the cells, are the 
following facts. There seems no close relation between 
the degree of increased secretion and that of aggre- 
gation. Thus a particle of sugar added to the secre- 
tion round a gland causes a much greater increase of 
secretion, and much less aggregation, than does a 
particle of carbonate of ammonia given in thé samo 
manner. It does not appear probable that pure water 
would cause much exosmose, and yet aggregation 
often follows from an immersion in water of between 
16 hrs. and 24 hrs., and always after from 24 hrs. to 
48 hrs. Still less probable is it that water at a tempe- 
rature of from 125° to 130° Fahr. (51°6 to 54°4 Cent.) 
should cause fluid to pass, not only from the glands, 
but from all the cells of the tentacles down to their 
bases, so quickly that aggregation is induced within 
2m. or 3 m. Another strong argument against 
this view is, that, after complete aggregation, the 
spheres and oval masses of protoplasm float about 
in an abundant supply of thin colourless fluid; so 
that at least the latter stages of the process cannot 
be due to the want of fluid to hold the protoplasm 
in solution. There is still stronger evidence that 
aggregation is independent of secretion; for the pa- 
pillz, described in the first chapter, with which the 
