CH. II] RESERVE MATERIALS. 15 



embryo contained in certain envelopes or wrappings. In 

 a dry seed this young plant is alive but it is a dormant, 

 quiescent form of life ; in a germinating seed it is on the 

 other hand actively alive, vigorously performing the func- 

 tions of a living thing, and on the high road to become 

 a full-grown plant. How is it that it is possible to 

 unlock the dormant energies of the bean-seed ? Certain 

 changes must be made in the surroundings of the seed. 

 In the first place it must be supplied with water. In the 

 laboratory beans are usually soaked for 12 to 24 hours, 

 during which time they absorb great quantities of water, 

 and increase considerably in weight and size. They change 

 in aspect, become softer and less brittle, while they no 

 longer show the wrinkled seed-coat characteristic of a dry 



Secondly, a certain degree of warmth is necessary. A 

 bean seed which has been soaked in water does not grow 

 if kept at a temperature of C. Nor does it grow if the 

 temperature is above 50 C. 



A third condition is also necessary, the seed must have 

 free oxygen, it must have access to the atmosphere, or at 

 least to air dissolved in water. If placed in an atmo- 

 sphere of some indifferent gas such as nitrogen or hydrogen 

 it will not grow. 



Respiration is necessary for the life of the seed, and 

 therefore for growth, which is one of the manifestations of 

 life. The respiration of plants is of the same nature as 

 that of animals : it is easy to illustrate this by a simple 

 experiment. A well-stoppered jar is partly filled with 

 germinating seeds; after 24 hours the stopper is cau- 



