ADJUSTMENT TO CHANGES IN TEMPERATURE 9 1 



Table Showing Critical Points in Temperature of 

 Representative Species. ' 



141. Adjustment to Changes in Temperature. The establish- 

 ment of a plant at any temperature, by enclosing it in a medium, 

 is not followed immediately by the activity characteristic of that 

 temperature ; some time is necessary to call up the effect. Thus 

 if an organism is at the minimum temperature, and is raised to 

 the optimum, it will be some hours before the beneficial change 

 will be followed by the usual rate of growth. If the tempera- 

 ture of the medium be raised or lowered gradually it is possible 

 for many organisms to become acclimatized, which entails the 

 adjustment of the three critical points. Such acclimatization 

 must consist chiefly in changes in the proteid bodies in proto- 

 plasm, and be connected with variations in the amount of water 

 of constitution present. 



142. Stimulating Influence of Changes in Temperature. Sud- 

 den changes in the intensity of the heat rays, or of the tempera- 

 ture of a plant constitute a stimulus which brings its own proper 

 response. These reactions may be due directly to the varied 

 chemical activity of the compounds in the protoplasm, or may 

 be adaptive responses on the part of living matter. 



J Data taken chiefly from Davenport's Exp. Morphology, r : 219. 1897. 



