146 PLANTS WHICH EXHIBIT MOVEMENTS IN THE CAPTURE OF PREY. 



one on one side and the other on the other. The movement of the tentacles is often 

 accompanies^, by an inflection of the whole surface of the leaf, the lamina becoming 

 concave like a hollow palm, and when, under these circumstances, the tentacles have 

 converged from the margin on to the concave central part, the leaf resembles a 

 closed fist (see fig. 26 ^). 



All these movements vary from one case to another and supplement one another 

 according to the needs of the moment and with a view to immediate advantage. 

 The one result that is always attained by the combined action is the covering of the 

 prey with a copious supply of the secretion poured from a number of glands, so that 

 it is dissolved and rendered fit for absorption and for the purposes of nourishment. 

 When an insect is caught by one of the marginal tentacles, the secretion there 

 discharged would not suffice for these purposes. The prey is accordingly trans- 

 ported as far as possible towards the middle of the lamina, where it comes into 

 contact with the digestive juice exuded from a maximum number of glands. It is 

 only when the size of the animal is rather large that the leaf becomes hollow in the 

 middle like a spoon, with the juice of more than fifty glands concentrated in the 

 depression. In a case of this kind the tentacles remain inflected much longer, 

 because the solution of the prey requires more time. If the captive is very small, 

 its solution and absorption are completed in a couple of days. Afterwards, the 

 tentacles lift, straighten themselves, and resume their original positions. The jaws, 

 wings, compound eyes, leg-bones, claws, &c., of the captured animals are left behind 

 undigested; but the flesh and blood are totally absorbed, and the liquid poured out 

 by the glands to effect solution is also re-imbibed by them. The undigested 

 remnants being now suspended on dry tentacles are easily blown away from the 

 sun-dew leaves by the wind. After an interval of a day or two the glands at the 

 ends of the tentacles, now occupying their original positions, again separate out a 

 viscid fluid in the form of tiny dewdrops, and the leaf is once more furnished 

 with the means of securing insects, and is able to repeat the movements above 

 described. 



Amongst the animals which fall victims to the sun-dew the most predominant 

 are little midges; but rather larger flies, too, ants both with and without wings, 

 beetles, small butterflies, and even dragon-flies, as they run, creep, or fly past, 

 adhere to the extended gland-bearing tentacles as though they were limed-twigs. 

 The larger animals, such as dragon-flies, are secured by the co-operation of two 

 or three adjacent leaves. Some idea of the large number of captives made by a 

 sun-dew is given by the fact that once upon a single leaf were found the remains of 

 thirteen different insects. 



In order to place in a true light the vast significance of the movements of the 

 tentacles belonging to Drosera leaves in relation, not only to the nourishment of 

 that plant, but to plant-life in general, it is necessary to direct attention to the 

 facts that these movements are accomplished not in the cell directly excited, but in 

 others, i.e. in adjacent cells belonging to the same community ; that a propagation of 

 the stimulus takes place from one protoplast to a second, thence to a third, fourth, 



