the open air, during which time the leaves, being of a red colour,
would have absorbed some oxygen. One of them, as well as a fresh leaf
for comparison, were now immersed in the same solution as before. The
former were looked at repeatedly, and after an interval of 65 m. a few
spheres of protoplasm were first observed in the cells close beneath
the glands, but only in two or three of the longer tentacles. After 3
hrs. the aggregation had travelled down the pedicels of a few of the
tentacles [page 60] for a length equal to that of the glands. On the
other hand, in the fresh leaf similarly treated, aggregation was plain
in many of the tentacles after 15 m.; after 65 m. it had extended down
the pedicels for four, five, or more times the lengths of the glands;
and after 3 hrs. the cells of all the tentacles were affected for
one-third or one-half of their entire lengths. Hence there can be no
doubt that the exposure of leaves to carbonic acid either stops for a
time the process of aggregation, or checks the transmission of the
proper influence when the glands are subsequently excited by carbonate
of ammonia; and this substance acts more promptly and energetically
than any other. It is known that the protoplasm of plants exhibits its
spontaneous movements only as long as it is in an oxygenated condition;
and so it is with the white corpuscles of the blood, only as long as
they receive oxygen from the red corpuscles;* but the cases above given
are somewhat different, as they relate to the delay in the generation
or aggregation of the masses of protoplasm by the exclusion of oxygen.
A Summary and Concluding Remarks. The process of aggregation is
independent of the inflection of the tentacles and of increased
secretion from the glands. It commences within the glands, whether
these have been directly excited, or indirectly by a stimulus received
from other glands. In both cases the process is transmitted from cell
to cell down the whole length of the tentacles, being arrested for a
short time at each transverse partition. With pale-coloured leaves the
first change which is perceptible, but only
* With respect to plants, Sachs, Traite de Bot. 3rd edit., 1874, p.
864. On blood corpuscles, see Quarterly Journal of Microscopical
Science, April 1874, p. 185. [page 61]
under a high power, is the appearance of the finest granules in the
fluid within the cells, making it slightly cloudy. These granules soon
53