454 



EFFECT OF HEAT 



[Ch. xvni 



Fig. 129, shows, more graphically than the tables from which 

 they are drawn, that, as the temperature rises, growth increases 

 up to a certain point, and then diminishes again. The falling 

 off is more rapid than the increase — a condition which we 

 found also in the curves (Fig. 68 ; p. 226) giving the rate of 

 movement of protoplasm at different temperatures. We have 

 thus three critical points to distinguish : the minimum, or 

 lowest temperature at which growth occurs ; the optimum, or 

 the temperature of greatest growth ; and the maximum, or the 

 highest temperature at which growth can take place. These 

 critical points, then, are to be considered comparatively ; and 

 as an introduction to this consideration I present, in a table, 

 the points as they have been determined for various species : — 



TABLE L 



Showing Critical Points for Various Plant Organisms, arranged 

 according to the optimum 



Name of Plant. 



Tempekatuke foe Growth. 



Optimitm. Minimum. Maximum, 



Bacillus phosphoresoens . . 



Penicillium 



Phaseolus inultiflorus (Eadicle) 

 Pisum sativum (Plumule) 

 Sinapis alba (Plum.) . . . 

 Lepidium sativum (Plum.) . 

 Linum usitatissimum (Plum.) 

 Lupinus albus (Plum.) . . . 

 Hordeum vulgare (Plum.) 



Triticum vulgare (Plum.) . . < 



Yeast . . 



Bacillus subtilis ... . . 

 Bacterium termo 



Zea mais (Plum.) 



Phaseolus multiflorus (Plum.) 

 Cucurbita pepo (Plum.) 

 Zea mais (Rad.) . . 

 Bacillus ramosus . . 



' ' anthracis . 



' ' tuberculosis 



" thermophilus 



20.0° 



22.0 



26.3 



26.6 



27.4 



27.4 



27.4 



28.0 



28.7 



28.7 



29.7 



28-34 

 30.0 



30-35 

 32.4 

 33.7 

 33.7 

 33.7 

 34.0 

 37.0 

 37.0 

 38.0 



63-70 



0.0° 

 1.5 



6.5 

 0.0 

 1.8 

 1.8 

 7.5 

 5.0 

 5.0 

 7.5 

 0.0 + 

 6.0 

 5.0 

 9.6 

 9.5 

 9.5 

 13.7 



13.0 

 14.0 

 30.0 

 42.0 



37.0° 

 43.0 



37.2 + 

 37.2 + 

 37.2 + 



37.7* 

 42.5 



38.0 

 50,0 

 40.0+ 



46.2 

 46.2 

 46.2 



40.0 

 45.0 

 42.0 

 72.0 



POKSTER, '87 

 WiESNER, '73 



Sachs 



KoPPEN 

 DE VkIES 



KoPPEN 



Sachs 



K6PPEN 



EiDAM, '75 

 KOppen 



Sachs 



Ward, '95 

 Fischer, '97 



