78 THE PLANT WORLD. 



if an insect lays foot upon the crest, he is quickly raised and 

 almost at once thrown forward into the calvx-cnp. W^ith the 

 labellum shut he finds himself in a shallow box with translucent 

 golden walls, veined with red. When he regains his feet and 

 turns about he sees light through a small opening. Climbing up, 

 he squeezes out past the end of the column (at c, Fig. 14). Here 

 he brushes against the sticky knobs of the pollen-masses, and takes 

 one or both of them away with him. If he visits a second flower 

 and is entrapped he may leave the pollen of the first flower upon 

 the adhesive stigmatic surface of the second, past which surface 

 he must crawl when again escaping. The case is in eft'ect very 

 like that of our moccasin flower, or lady's slipper. 



The motility of this labellum reminds one also of the similar 

 powers of barberry stamens, which spring together so suddenly 

 upon having their filaments touched. 



It is interesting to find that other stimuli besides contact are 

 capable of springing the lip. I found that moving the lip back- 

 ward and forward upon the hinge, without touching the sensitive 

 ridge, produces the efifect. When the plant was carried out of doors 

 into a temperature of 46° F. the lip immediately closed. When 

 drops of water fell on the lip it closed, probably from sudden 

 change of temperature. A red-hot needle w^as held near the 

 cushion with the same result. Discharge of electric sparks oper- 

 ated in the same way, but it is not certain — though probable 

 enough — that the effect was a purely electrical one. About an 

 hour after night-fall the lip folded up of its own accord ; before 

 light next morning ( 5 : 30 a. m., December 23) it was open again. 

 This action is periodic and diurnal. Darkening the plant in the 

 daytime had no effect. 



A side sectional view shows that the movement results from the 

 flexure of the neck (Fig. 14, /; ). In fact, as there are no tendons 

 and no transmission of power, the motors must be located here. 

 But the stimulus is received by the crest, which is at a little dis- 

 tance from the hinge. Wlien the surface cells of the crest are 

 pressed by an insect's foot, changes, the nature of which is un- 

 known, take place in their contents, which cause changes in under- 

 lying cells, and these affect in turn the next cells, an impulse thus 



