372 PINGUICDLA VULGARIS. Chap. XVI. 



After 4 hrs. 20 m. there was decided incurvation, whicli in- 

 creased 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 reckoning from the time when the flies were 

 placed on the leaf) the margin had everywhere begun 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 mar- 

 gins were perceptibly incurved in 3 hrs., and after 4 hrs. 20 m. 

 to such a degi'ee 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 affected) 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.) apai't, 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 aft-.rwards 

 re-expanded ; but the meat did not cause even a trace of incur- 

 vation. 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 

 midrib and one margin. A short space of this margin, opposite 

 the fly, showed a trace of incuiwation after 3 hrs,, and this 

 became strongly pronounced in 7 hrs. After 24 hrs. the infolded 

 edge was only -16 of an inch (4-064 mm.) from the midrib. 

 The margin now began to unfold, though the fly was left on the 

 leaf; so that by the next morning (i.e. 48 hrs. from the time 

 when the fly was first put on) the infolded edge had almost 

 completely recovered its original position, being now '3 of an 

 inch (7*62 mm.), instead of -16 of an inch, from the midrib. 

 A trace of flexure was, however, still visible. 



Experiment 6. — A young and concave leaf was selected with 

 its margins slightly and naturally incurved. Two rather large, 

 oblong, rectangular pieces of roast meat were placed with their 

 ends touching the infolded edge, and ^G of an inch (11-68 mm.) 



