22 Life and Immortality. 



according to the size of the leaf, are left open for a short 

 time before the edges of the lobes come into contact, 

 consequent upon the intercrossing of the tips of the mar- 

 ginal spikes first, thus enabling an insect whose body is not 

 thicker than these measurements to escape, when disturbed 

 by the closing lobes and the increasing darkness, quite easily 

 between the crossed spikes. Moderately sized insects, if they 

 try to escape between the bars, will be pushed back into the 

 horrid prison with the slowly closing walls, for the spikes 

 continue to close more and more until the lobes are brought 

 into contact. Very strong insects, however, manage to effect 

 their release. It would manifestly be a great disadvantage 

 to the plant to remain many days clasped over a minute 

 insect, and as many additional days or weeks in recovering 

 its sensibility, inasmuch as a very small insect would afford 

 but little nourishment. Far better would it be for the plant 

 to wait until a moderately large insect was captured, and to 

 allow the little ones to escape, and this advantage is gained 

 by the slow intercrossing of the marginal spikes, which, 

 acting like the large meshes of a fishing-net, allow the small 

 and worthless fry to pass through. 



Touching any one of the six filaments is sufficient to 

 cause both lobes to close, these becoming at the instant 

 incurved throughout their entire breadth. The stimulus 

 must therefore radiate in all directions from any one fila- 

 ment, and it must also be transmitted with considerable 

 rapidity across the leaf, for in all ordinary cases, as far as the 

 eye can judge, both lobes close at the same time. Physiolo- 

 gists generally believe that in irritable plants the excitement 

 is transmitted along, or in close connection with, the fibro- 

 vascular bundles. Those in Dionaea seem at first sight to 

 favor this belief, for they run up the mid- rib in a great bun- 

 dle, sending off small bundles almost at right angles on each 

 side, which bifurcate occasionally as they stretch towards 

 the margin, the marginal branches from adjoining branches 

 uniting and entering the marginal spikes. Thus a continuous 



