Scientific lectures / by Sir John Lubbock.

Date:
1879
Catalogue details

Licence: Public Domain Mark

Credit: Scientific lectures / by Sir John Lubbock. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the plant catches and devours the insects.^ The first observation on insect-eating flowers was made about the year 1768 by our countryman Ellis. He observed that in Dionaea, a North American plant, the leaves have a joint in the middle, and thus close over, kill, and actu- ally digest any insect which may alight on them. In our Common Sundew {Drosera rotundifolia, Fig. 4) the rounded leaves are covered with glutinous glandular in the glutinous secretion, the glands close over it, ^ their secretion is increased, and they literally digest their prey. Mr. Frank Darwin has recently shown that plants supplied with insects grow more vigorously than those not so fed. It is very curious that while the glands are so sensitive that even an object weighing only ^^^th of a grain placed on them is sufficient to cause motion, yet they are insensible to the weight and repeated blows of dropsof even heavy rain. Drosera, however, is not our only English insect- Fig. 4.—Brosem rotundifolia. hairs or tentacles—on an average about 200 on a full-sized leaf. The glands are each surrounded by a drop of an exceedingly Auseid solution, which, glittering in the sun, has given rise to the name of the plant. If any object be placed on the leaf, these glandular hairs slowly fold over it, but if it be inorganic they soon unfold again. On the other hand, if any small insect alights on the leaf it becomes entanffied O ^ See Darwin’s Insectivorous Plants.
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