Chap. IV. THE EFFECTS OF HEAT. 69 



ammonia, and the glands quickly became black, with strongly 

 marked aggregation in the tentacles, showing that the proto- 

 plasm was alive, and that the glands had not lost their power of 

 absorption. Another leaf was placed in water at 110^ (43"-3 

 Cent.) w^hich was raised to 120° (48°-8 Cent.) ; and every ten- 

 tacle, excepting one, was quickly and closely inflected. This leaf 

 was now immersed in a few drops of a strong solution of car- 

 bonate of ammonia (one i3art to 109 of water) ; in 10 m. all the 

 glands became intensely black, and in 2 hrs. the protoplasm in 

 the cells of the pedicels was well aggregated. Another leaf was 

 suddenly plunged, and as usual waved about, in water at 120°, 

 and the tentacles became inflected in from 2 m, to 3 m., but 

 only so as to stand at right angles to the disc. The leaf was 

 now placed in the same solution (viz. one part of carbonate of 

 ammonia to 109 of water, or 4 grs. to 1 oz., which I will for 

 the future designate as the strong solution), and when I looked 

 at it again after the interval of an hour, the glands were 

 blackened, and there was well-marked aggregation. After an 

 additional interval of 4 hrs. the tentacles had become much 

 more inflected. It deserves notice that a solution as strong as 

 this never causes inflection in ordinary cases. Lastly a leaf 

 was suddenly placed in water at 125° (51°-6 Cent.), and was 

 left in it until the water cooled ; the tentacles were rendered 

 of a bright red and soon became inflected. The contents of 

 the cells underwent some degree of aggregation, which in 

 the course of three hours increased ; but the masses of proto- 

 plasm did not become spherical, as almost always occurs with 

 leaves immersed in a solution of carbonate of ammonia. 



We learn from these cases tliat a temperature of 

 from 120° to 125° (48°-8 to 5r-6 Cent.) excites the 

 tentacles into quick movement, but does not kill the 

 leaves, as shown either by their subsequent re-expansion 

 or by the aggregation of the protoplasm. We shall 

 now see that a temperature of 1*30° (54°4 Cent.) is too 

 high to cause immediate inflection, yet does not kill 

 the leaves. 



Experiment 1. — A leaf was plunged, and as in all cases 

 waved about for a few minutes, in water at 130° (54° '4 Cent.), 

 but there was no trace of inflection; it was then placed in cold 

 water, and after an interval of 15 m. very slow movement was 



