310 SOILS. 



low which most cultivated plants may be considered as remain- 

 ing practically inactive lies between 4.4 and 7.2 C. (40 and 

 45 F.). Few tropical plants will germinate much below 

 23.8 (75 F.) and in some cases not below 35 Cent. (95 

 F.). Even maize and pumpkins, according to Haberlandt, 

 germinate most rapidly between 35 and 38.3 C. (95 and 101 

 F.), while for wheat, rye, oats and flax the best temperature 

 for germination lies between 21.1 to 26.1 (70 to 79). Un- 

 der the most favorable conditions of temperature and moisture, 

 some small seeds which readily absorb moisture will germinate 

 in from twenty-four to forty-eight hours, while at a lower 

 temperature they may require from three days to two weeks. 

 Thus Haberlandt found that while oats would germinate in 

 two days at a temperature of 17.2 to 17.5 C. (63 to 63.5), 

 it took a full week for germination when the temperature was 

 only 5 C. (41 F.). It is obvious that seeds remaining inert 

 in the soil for such lengths of time will be subject to a variety 

 of vicissitudes that may injure or destroy their vitality. There 

 are many bacteria and fungous parasites which at low tem- 

 peratures are perfectly capable of attacking and destroying the 

 water-soaked seed. There is thus for each plant, from the 

 lowest to the highest, a certain temperature most favorable to 

 development; and both above and below this, the vegetative 

 activity is seriously interfered with or wholly checked. A 

 knowledge of these limits is manifestly of the utmost practical 

 importance. 



The influence of too high a temperature in preventing the germina- 

 tion of cinchona seed from India, was curiously exemplified when it 

 was subjected to a supposedly favorable steady temperature of 23.8C. 

 (75F.) under otherwise most favorable conditions. Not a single one 

 came up in the course of six weeks, and the box in which it had been 

 sown was put away outside of the hothouse as a failure. Within two 

 weeks a full stand of seedlings was obtained, at temperatures ranging 

 between 12.7 and i5.5C. (55 and 6oF.). The fact that the cinchona 

 is a tree of the lower slopes of the Andes (three to five thousand feet) 

 although at home strictly within the tropics, explains the apparent 

 anomaly. 



