(8) Five very small bits of gluten were placed on a leaf, and they
excited so much secretion that one of the bits glided down into the
marginal furrow. After a day all five bits seemed much reduced in size,
but none were wholly dissolved. On the third day I pushed two of them,
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.
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