Insectivorous Plants eBook

This eBook from the Gutenberg Project consists of approximately 527 pages of information about Insectivorous Plants.
other glands were touched with a little saliva, and the tentacles became incurved in under 1 hr., and re-expanded after 18 hrs.  Particles of glass, cork, cinders, thread, and gold-leaf, were placed on numerous glands on two leaves; in about 1 hr. four tentacles became curved, and four others after an additional interval of 2 hrs. 30 m.  I never once succeeded in causing any movement by repeatedly touching the glands with a needle; and Mrs. Treat made similar trials for me with no success.  Small flies were placed on several leaves near their tips, but the thread-like blade became only on one occasion very slightly bent, directly beneath the insect.  Perhaps this indicates that the blades of vigorous plants would bend over captured insects, and Dr. Canby informs me that this is the case; but the movement cannot be strongly pronounced, as it was not observed by Mrs. Treat.

Drosera binata (or dichotoma).—­I am much indebted to Lady

* ‘American Naturalist,’ December 1873, page 705. [page 282]

Dorothy Nevill for a fine plant of this almost gigantic Australian species, which differs in some interesting points from those previously described.  In this specimen the rush-like footstalks of the leaves were 20 inches in length.  The blade bifurcates at its junction with the footstalk, and twice or thrice afterwards, curling about in an irregular manner.  It is narrow, being only 3/20 of an inch in breadth.  One blade was 7 1/2 inches long, so that the entire leaf, including the footstalk, was above 27 inches in length.  Both surfaces are slightly hollowed out.  The upper surface is covered with tentacles arranged in alternate rows; those in the middle being short and crowded together, those towards the margins longer, even twice or thrice as long as the blade is broad.  The glands of the exterior tentacles are of a much darker red than those of the central ones.  The pedicels of all are green.  The apex of the blade is attenuated, and bears very long tentacles.  Mr. Copland informs me that the leaves of a plant which he kept for some years were generally covered with captured insects before they withered.

The leaves do not differ in essential points of structure or of function from those of the previously described species.  Bits of meat or a little saliva placed on the glands of the exterior tentacles caused well-marked movement in 3 m., and particles of glass acted in 4 m.  The tentacles with the latter particles re-expanded after 22 hrs.  A piece of leaf immersed in a few drops of a solution of one part of carbonate of ammonia to 437 of water had all the glands blackened and all the tentacles inflected in 5 m.  A bit of raw meat, placed on several glands in the medial furrow, was well clasped in 2 hrs. 10 m. by the marginal tentacles on both sides.  Bits of roast meat and small flies did not act quite so quickly; and albumen and fibrin still less quickly.  One of the bits of meat excited so much secretion (which is always acid) that it flowed some way down the medial furrow, causing the inflection of the tentacles on both sides as far as it extended.  Particles of glass placed on the glands in the medial furrow did not stimulate them sufficiently for any motor impulse to be sent to the outer tentacles.  In no case was the blade of the leaf, even the attenuated apex, at all inflected.

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Insectivorous Plants from Project Gutenberg. Public domain.
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