86 BACTERIA IN RELATION TO PLANT DISEASES. 
2. é., commonest in southern Italy, Sicily, and Algeria, lies between 32° and 38°C. 
In my own experiments with this organism, obtained from olive trees in California, 
I have found its maximum temperature to be above 35° and below 37.5° C. The 
optimum temperature of Bacterium solanacearum, which is very destructive to 
potatoes and tomatoes in the southern United States, is probably about 35° C.—at 
least it grew readily and remained alive for a long time in bouillon kept at 37° C. 
Its maximum temperature is 39 +°C. Bacillus carotovorus, one of the best known 
of the soft-rot organisms, grows well in the thermostat at 33° to 34°C. Its maxi- 
mum temperature is at 39° C. or slightly below (Jones). Bacillus aroidee, whose 
temperature relations were recently studied carefully by Townsend, has a maximum 
temperature of 41° C. A temperature of 40° C. retards growth, but does not prevent 
it. This organism was isolated from calla-lily corms, but is capable of causing a 
soft rot in potatoes, carrots, turnips, and many other plants (fig. 102). The maxi- 
mum temperature of Bacillus oleraceae, recently described by Harrison, is said to 
be about 42° C. ‘This causes a soft rot of cauliflower. 
The range of temperature suited for the growth of particular bacteria varies 
greatly. Some species are able to grow through a range of 50° C. Many tolerate 
a range of only about 30° C. Certain animal-pathogenic forms have through long 
subjection to a peculiar environment become restricted to a still narrower range. 
*Fic, 71.—Bacterium pruni, Early stage of a leaf-spot in the plum, The small spot was water- 
soaked in appearance, but it had not yet collapsed. ‘The bacteria, which are most abundant in the 
mesophyll, undoubtedly entered the leaf through the stomata, three of which are shown in the section. 
Material treated as in fig. 70. Section drawn with the aid of an Abbe camera. It represents as 
nearly as possible one plane. 
