which had begun to dry, on to fresh glands. On the fourth day
undissolved traces of three out of the five bits could still be
detected, the other two having quite disappeared; but I am doubtful
whether they had really been completely dissolved. Two fresh bits were
now placed, one near the middle and the other near the margin of
another leaf; both excited an extraordinary amount of secretion; that
near the margin had a little pool formed round it, and was much more
reduced in size than that on the blade, but after four days was not
completely dissolved. Gluten, therefore, excites the glands greatly,
but is dissolved with much difficulty, exactly as in the case of
Drosera. I regret that I did not try this substance after having been
immersed in weak hydrochloric acid, as it would then probably have been
quickly dissolved.
(9) A small square thin piece of pure gelatine, moistened with water,
was placed on a leaf, and excited very little secretion in 5 hrs. 30
m., but later in the day a greater amount. After 24 hrs. the whole
square was completely liquefied; and this would not have occurred had
it been left in water. The liquid was acid.
(10) Small particles of chemically prepared casein excited [page 384]
acid secretion, but were not quite dissolved after two days; and the
glands then began to dry. Nor could their complete dissolution have
been expected from what we have seen with Drosera.
(11) Minute drops of skimmed milk were placed on a leaf, and these
caused the glands to secrete freely. After 3 hrs. the milk was found
curdled, and after 23 hrs. the curds were dissolved. On placing the now
clear drops under the microscope, nothing could be detected except some
oil-globules. The secretion, therefore, dissolves fresh casein.
(12) Two fragments of a leaf were immersed for 17 hrs., each in a
drachm of a solution of carbonate of ammonia, of two strengths, namely
of one part to 437 and 218 of water. The glands of the longer and
shorter hairs were then examined, and their contents found aggregated
into granular matter of a brownish-green colour. These granular masses
were seen by my son slowly to change their forms, and no doubt
consisted of protoplasm. The aggregation was more strongly pronounced,
and the movements of the protoplasm more rapid, within the glands
subjected to the stronger solution than in the others. The experiment
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