Insectivorous Plants eBook

This eBook from the Gutenberg Project consists of approximately 462 pages of information about Insectivorous Plants.

[A friend sent me on June 23 thirty-nine leaves from North Wales, which were selected owing to objects of some kind adhering to them.  Of these leaves, thirty-two had caught 142 insects, or on an average 4.4 per leaf, minute fragments of insects not being included.  Besides the insects, small leaves belonging to four different kinds of plants, those of Erica tetralix being much the commonest, and three minute seedling plants, blown by the wind, adhered to nineteen of the leaves.  One had caught as many as ten leaves of the Erica.  Seeds or fruits, commonly of Carex and one of Juncus, besides bits of moss and other rubbish, likewise adhered to six of the thirty-nine leaves.  The same friend, on June 27, collected nine plants bearing seventy-four leaves, and all of these, with the exception of three young leaves, had caught insects; thirty insects were counted on one leaf, eighteen on a second, and sixteen on a third.  Another friend examined on August 22 some plants in Donegal, Ireland, and found insects on 70 out of 157 leaves; fifteen of [page 370] these leaves were sent me, each having caught on an average 2.4 insects.  To nine of them, leaves (mostly of Erica tetralix) adhered; but they had been specially selected on this latter account.  I may add that early in August my son found leaves of this same Erica and the fruits of a Carex on the leaves of a Pinguicula in Switzerland, probably Pinguicula alpina; some insects, but no great number, also adhered to the leaves of this plant, which had much better developed roots than those of Pinguicula vulgaris.  In Cumberland, Mr. Marshall, on September 3, carefully examined for me ten plants bearing eighty leaves; and on sixty-three of these (i.e. on 79 per cent.) he found insects, 143 in number; so that each leaf had on an average 2.27 insects.  A few days later he sent me some plants with sixteen seeds or fruits adhering to fourteen leaves.  There was a seed on three leaves on the same plant.  The sixteen seeds belonged to nine different kinds, which could not be recognised, excepting one of Ranunculus, and several belonging to three or four distinct species of Carex.  It appears that fewer insects are caught late in the year than earlier; thus in Cumberland from twenty to twenty-four insects were observed in the middle of July on several leaves, whereas in the beginning of September the average number was only 2.27.  Most of the insects, in all the foregoing cases, were Diptera, but with many minute Hymenoptera, including some ants, a few small Coleoptera, larvae, spiders, and even small moths.]

We thus see that numerous insects and other objects are caught by the viscid leaves; but we have no right to infer from this fact that the habit is beneficial to the plant, any more than in the before given case of the Mirabilis, or of the horse-chestnut.  But it will presently be seen that dead insects and other nitrogenous bodies excite the glands to increased secretion; and that the secretion then becomes acid

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Insectivorous Plants from Project Gutenberg. Public domain.
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