if they had been in contact with insects; whilst the other glands on
the same leaves contained only clear homogeneous fluid.
(15) Seeds. A considerable number of seeds or fruits selected by
hazard, some fresh and some a year old, some soaked for a short time in
water and some not soaked, were tried. The ten following kinds, namely
cabbage, radish, Anemone nemorosa, Rumex acetosa, Carex sylvatica,
mustard, turnip, cress, Ranunculus acris, and Avena pubescens, all
excited much secretion, which was in several cases tested and found
always acid. The five first-named seeds excited the glands more than
the others. The secretion was seldom copious until about 24 hrs. had
elapsed, no doubt owing to the coats of the seeds not being easily
permeable. Nevertheless, cabbage seeds excited some secretion in 4 hrs.
30 m.; and this increased so much in 18 hrs. as to run down the leaves.
The seeds or properly the fruits of Carex are much oftener found
adhering to leaves in a state of nature than those of any other genus;
and the fruits of Carex sylvatica excited so much secretion that in 15
hrs. it ran into the incurved edges; but the glands ceased to secrete
after 40 hrs. On the other hand, the glands on which the seeds of the
Rumex and Avena rested continued to secrete for nine days.
The nine following kinds of seeds excited only a slight amount of
secretion, namely, celery, parsnip, caraway, Linum grandiflorum,
Cassia, Trifolium pannonicum, Plantago, onion, [page 386] and Bromus.
Most of these seeds did not excite any secretion until 48 hrs. had
elapsed, and in the case of the Trifolium only one seed acted, and this
not until the third day. Although the seeds of the Plantago excited
very little secretion, the glands continued to secrete for six days.
Lastly, the five following kinds excited no secretion, though left on
the leaves for two or three days, namely lettuce, Erica tetralix,
Atriplex hortensis, Phalaris canariensis, and wheat. Nevertheless, when
the seeds of the lettuce, wheat, and Atriplex were split open and
applied to leaves, secretion was excited in considerable quantity in 10
hrs., and I believe that some was excited in six hours. In the case of
the Atriplex the secretion ran down to the margin, and after 24 hrs. I
speak of it in my notes as immense in quantity and acid. The split
seeds also of the Trifolium and celery acted powerfully and quickly,
though the whole seeds caused, as we have seen, very little secretion,
and only after a long interval of time. A slice of the common pea,
which however was not tried whole, caused secretion in 2 hrs. From
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