282 



LECTURE XIII. 



they were exposed to a dry heat for an hour. They were afterwards 

 sown in earth. In the table, A indicates that the seedlings appeared 

 above the surface of the soil ; B that, though the seeds germinated, the 

 seedlings did not reach the surface : the blank spaces indicate that no 

 germination took place : a dash indicates that no determination was 

 made. The numbers are percentages. 



i. Dry seeds : 



Soaked seeds : 



It has been occasionally observed that seeds survive pro- 

 longed boiling in water, for example, that the seeds in the 

 stones of plums which have been made into jam may germi- 

 nate. This is due to the fact that the seeds are protected 

 from the action of the hot water by the thick endocarp. 



The observations which have been made as to the effect of 

 high temperatures upon spores fully accord with those stated 

 above with reference to seeds. Pasteur has shewn that dry 

 spores of Penicillum glaucum can endure, without injury, 

 a temperature of 108 C., and that the majority germinate 

 after being exposed to a temperature of 1 19 121 C. for half- 

 an-hour. They are all killed by half-an-hour's exposure to a 



