THE POWER OR ENERGY OF THE PLANT 185 



is this slow burning up of the protoplasm which is 

 responsible for the death of old seeds. At extremely 

 low temperatures it ceases, as do all the activities 

 of protoplasm. Thus when seeds are placed in 

 liquid air at a temperature of nearly three hundred 

 degrees below zero, Fahrenheit, it can be stated 

 with certainty that breathing as well as all other 

 activities have ceased. 



225. Changes in the air produced by breathing. — 

 The oxygen used in breathing is sometimes taken 

 from compounds in the plant, and then the burn- 

 ing is sometimes incomplete, and no external evi- 

 dence of it can be seen. In one form, however, 

 marked changes are made in the air. This may be 

 detected by the following experiment. Secure three 

 fruit jars and fill one half-full of peas which have 

 been soaked in water for a day, put the same 

 quantity of dried peas in the second, and allow 

 the third to remain empty. Cover tightly. A day 

 later prepare a small torch by fastening a section of 

 a candle an inch long to a piece of wire a foot long. 

 A bit of string soaked in oil will answer equally 

 well. Light the torch, remove the cover of the 

 empty jar, and lower the blaze into it. The flame 



