. IV. THE EFFECTS OF HEAT. 67 



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 ten- 

 tacles 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 car- 

 bonate 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. Considering that the tentacles are extremely 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 sensitiveness to heat. 



It will be convenient first briefly to describe tb.3 effects of 

 immersion for thirty seconds in boiling water. The leaves are 

 rendered 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 surfaces retain the power of contraction. The 

 purple fluid within the cells of the pedicels is rendered finely 

 granular, but there is no true aggregation ; nor does this follow 



altered by a very brief expo- able differences in this respect is 



enre to a temperature of 118 not surprising, considering that 



Fahr. as a maximum." As my some low vegetable organisms 



results are deduced from special grow in hot springs cases of 



phenomena, namely, the subse- which have been collected by 



quent aggregation of the proto- Prof. Wyman (' American Journal 



plasm and the re-expansion of of Science,' vol. xliv. 1867). Thus, 



the tentacles, they seem to me Dr. Hooker found Confervse in 



worth giving. We shall find that water at 1 (J8 Fahr. ; Humboldt, 



Drosera resists heat somewhat at 185 Fahr. ; and Descloizeaux, 



better than most other plants. at 208 Fahr. 

 That there should be consider- 



