524: Dynamic Theory. 



the organs of touch, for whenever they are touched by an appropriate 

 object, as the legs or wings of an insect, the lobes of the trap fly shut, 

 and generally catch the unlucky trespasser. The inner surfaces of the 

 lobes are covered with small glands of a reddish or purplish color, in 

 consequence of being composed of cells which are filled with a reddish 

 fluid. These minute glands stand on very short pedicels. When a cap- 

 ture is made, these glands secrete a fluid, which is colorless, slightly 

 mucilaginous, and quite acid. This secretion does not take place unless 

 the glands are brought into contact with nitrogenous matter. When the 

 lobes are closed upon an insect, or a bit of albumen or meat, the digest- 

 ible portion is completely dissolved and absorbed by the plant, which 

 takes several days for the process. But if the trap is excited to close 

 itself by an insect which nevertheless makes its escape, or by an arti- 

 ficial stimulus, which leaves no food to be digested, it opens within 24 

 hours. The lobes of the trap are about half an inch, or a little more, 



in length, and they manage very often 

 to catch beetles, spiders, &c. , half as 

 long as themselves. The closure of 

 the lobes together, is due to the con- 

 traction of the cells on the inner 

 faces of the lobes, and especially 

 those near the midrib. The stimula- 

 tion by which their action is excited, 

 spreads rapidly from any one of the 

 sensitive filaments, so that both lobes 

 engage in the movement of closing 

 at the same time. Dr. Burdon San- 

 derson discovered that there is a ' 'nor- 

 electric current in the blade and 



FIG. 248 . Exp andec 

 cipula. m. Midrib. 



foot-stalk, and that when the leaves are irritated the current is disturbed 

 in the same manner as takes place during the contraction of the muscle 

 of an anima.1." Both lobes of the trap of the Dionea will close when 

 any one of the six sensory filaments is touched, which shows that the 

 stimulus spreads in all directions through the cellular tissues of the 

 plant. And it crosses from one lobe to the other with great rapidity, 

 for both close at once. Darwin's experiments failed to find any other 

 organs than the cells themselves, that appear to be concerned in the 

 transmission of the stimulus. The vessels do not transmit it, or at 

 least not exclusively. Here then we have nervous transmission through 

 tissues not yet differentiated into nerves, just as we have it in Coelen- 

 terate animals. Other observers have agreed with Darwin that the 

 stimulation passes from cell to cell, not only in the Dionea but in Aldro- 

 vanda and Drosera as well. 



