surrounding the bags, and these travel much more quickly. That the
small spheres are separate is often shown by sometimes one and then
another travelling in advance, and sometimes they revolve round each
other. I have occasionally seen spheres of this kind proceeding up and
down the same side of a cell, instead of round it. The bag-like masses
after a time generally divide into two rounded or oval masses, and
these undergo the changes shown in figs. 7 and 8. At other times
spheres appear within the bags; and these coalesce and separate in an
endless cycle of change.
After leaves have been left for several hours in a solution of the
carbonate, and complete aggregation has been effected, the
* With other plants I have often seen what appears to be a true
shrinking of the primordial utricle from the walls of the cells, caused
by a solution of carbonate of ammonia, as likewise follows from
mechanical injuries. [page 47]
stream of protoplasm on the walls of the cells ceases to be visible; I
observed this fact repeatedly, but will give only one instance. A pale
purple leaf was placed in a few drops of a solution of one part to 292
of water, and in 2 hrs. some fine purple spheres were formed in the
upper cells of the pedicels, the stream of protoplasm round their walls
being still quite distinct; but after an additional 4 hrs., during
which time many more spheres were formed, the stream was no longer
distinguishable on the most careful examination; and this no doubt was
due to the contained granules having become united with the spheres, so
that nothing was left by which the movement of the limpid protoplasm
could be perceived. But minute free spheres still travelled up and down
the cells, showing that there was still a current. So it was next
morning, after 22 hrs., by which time some new minute spheres had been
formed; these oscillated from side to side and changed their positions,
proving that the current had not ceased, though no stream of protoplasm
was visible. On another occasion, however, a stream was seen flowing
round the cell-walls of a vigorous, dark-coloured leaf, after it had
been left for 24 hrs. in a rather stronger solution, namely, of one
part of the carbonate to 218 of water. This leaf, therefore, was not
much or at all injured by an immersion for this length of time in the
above solution of two grains to the ounce; and on being afterwards left
41