Chap. XVI.] MOVEMENTS OF THE LEAVES. 



301 



next day, after 15 hrs., this margin, but not the other, was found 

 folded inwards, like the helix of the human ear, to the breadth 

 of -^ of an inch, so as to lie partly over the row of flies (Fig. 15). 

 The glands on which the flieS rested, as well as those on the over- 

 lapping margin which had been brought into contact with the flies, 

 were all secreting copiously. 



Experiment 2. A row of flies was placed on one margin of a 

 rather old leaf, which lay flat on the ground; and in this case 

 the margin, after the same interval as before, namely 15 hrs., had 

 only just begun to curl inwards; but so much secretion had been 

 poured forth that the spoon-shaped tip of the leaf was filled with it. 



Experiment 3. Fragments of a large fly were placed close to 

 the apex of a vigorous leaf, as well as along half one margin. 

 After 4 hrs. 20 m. there was decided incurvation, which increased 

 a little during the afternoon, but was in the 

 same state on the following morning. Near 

 the apex both margins were inwardly curved. 

 I have never seen a case of the apex itself 

 being in the least curved towards the base 

 of the leaf. After 48 hrs. (always reckon- 

 ing from the time when the flies were placed 

 on the leaf) the margin had everywhere be- 

 gun to unfold. 



Experiment 4- A large fragment of a fly 

 Was placed on a leaf, in a medial line, a little 

 beneath the apex. Both lateral margins were 

 perceptibly incurved in 3 hrs., and after 4 

 hrs. 20 m. to such a degree that the fragment 

 was clasped by both margins. After 24 hrs. 

 the two infolded edges near the apex (for 

 the lower part of the leaf was not at all af- 

 fected) were measured and found to be .11 

 of an inch (2.795 mm.) apart. The fly was 

 now removed, and a stream of water poured 

 over the leaf so as to wash the surface; and 

 after 24 hrs. the margins were .25 of an inch 

 (6.349 mm.) apart, so that they were largely 

 unfolded. After an additional 24 hrs. they 

 were completely unfolded. Another fly was now put on the same 

 spot to see whether this leaf, on which the first fly had been 

 left 24 hrs., would move again; after 10 hrs. there was a trace of 

 incurvation, but this did not increase during the next 24 hrs. A 

 bit of meat was also placed on the margin of a leaf, which four 

 days previously had become strongly incurved over a fragment of 

 a fly and had afterwards re-expanded ; but the meat did not cause 

 even a trace of incurvation. On the contrary, the margin became 

 somewhat reflexed, as if injured, and so remained for the three 

 following days, as long as it was observed. 



Experiment 5. A large fragment of a fly was placed halfway 

 between the apex and base of a leaf and halfway between the mid- 

 rib and one margin. A short space of this margin, opposite the 



Fig. 15. 



(Pinguicula vulgaris.) 



Outline of leaf with 



left margin inflected 



over a row of small 



flies. 



