CuAP. IV.] THE EFFECTS OF HEAT. 57 



My experiments were tried in the following manner. Leaves 

 were cut off, and this does not in the least interfere with their 

 powers; for instance, three cut-off leaves, with bits of meat placed 

 on them, were kept in a damp atmosphere, and after 23 hrs. closely 

 embraced the meat both with their tentacles and blades; and the 

 protoplasm within their cells was well aggregated. Three ounces 

 of doubly distilled water was heated in a porcelain vessel, with a 

 delicate thermometer having a long bulb obliquely suspended in it. 

 The water was gradually raised to the required temperature by a 

 spirit-lamp moved about under the vessel ; and in all cases the 

 leaves were continually waved for some minutes close to the bulb. 

 They were then placed in cold water, or in a solution of carbonate 

 of ammonia. In other cases they were left in the water, which 

 had been raised to a certain temperature, until it cooled. Again, 

 in other cases the leaves were suddenly plunged into water of a 

 certain temperature, and kept there for a specified time. Consider- 

 ing that the tentacles are extremelj' delicate, and that their coats 

 are very thin, it seems scarcely possible that the fluid contents 

 of their cells should not have been heated to within a degree or 

 two of the temperature of the surrounding water. Any further 

 precautions would, I think, have been superfluous, as the leaves 

 from age or constitutional causes differ slightly in their sensitive- 

 ness to heat. 



It will be convenient first briefly to describe the effects of im- 

 mersion for thirt}"^ seconds in boiling water. The leaves are ren- 

 dered flaccid with their tentacles bowed backwards, which, as we 

 shall see in a future chapter, is probably due to their outer surfaces 

 retaining their elasticity for a longer period than their inner sur- 

 faces retain the power of contraction. The purple fluid within 

 the cells of the pedicels is rendered flnely granular, but there is 

 no true aggregation ; nor does this follow wheifl the leaves are sub- 

 sequently placed, in a solution of carbonate of ammonia. But the 

 most remarkable change is that the glands become opaque and 

 uniformly white; and this may be attributed to the coagulation 

 of their albuminous contents. 



My first and preliminary experiment consisted in putting seven 

 leaves in the same vessel of water, and warming it slowly up to the 

 temperature of 110 Fahr. (43''.3 Cent.); a leaf being taken out 

 as soon as the temperature rose to 80" (26''.6 Cent.), another at 

 85, another at 90, and so on. Each leaf when taken out, was 

 placed in water at the temperature of my room, and the tentacles 

 of all soon became slightly, though irregularly, inflected. They 

 were now removed from the cold water and kept in damp air, with 

 bits of meat placed on their discs. The leaf which had been ex- 

 posed to the temperature of 110 became in 15 ni. greatly in- 

 flected; and in 2 hrs. every single tentacle closely embraced the 

 meat. So it was, but after rather longer intervals, with the six 

 other leaves. It appears, therefore, that the warm bath had in- 

 creased their sensitiveness when excited by meat. 



I next observe<l the degree of inflection which leaves underwent 

 within stated periods, whilst still immersed in warm water, kept as 



