2 PLANT LIFE. 



bring about this change in protoplasm, and consequently 

 indirectly destroy life, inasmuch as the protoplasm has lost 

 its individuality, due to a chemical or physical change having 

 taken place in its composition. From what has been said 

 it will be seen that life is a force that can only manifest 

 itself through matter, and in so far agrees with chemical 

 and physical forces. Differences of degree are observable in 

 the manifestation of the various known forces ; for example, 

 the attraction of mass for mass, or gravitation, acts univers- 

 ally on all matter regardless of its chemical or physical 

 condition ; magnetism, on the other hand, is more restricted, 

 and its pecuUarities are more readily demonstrated through 

 iron than through wood ; whereas life, as already stated, 

 only manifests itself through one substance, protoplasm. 



The reason why life is met with under such varied and 

 extreme conditions depends on the fact that protoplasm 

 possesses the power of retaining its individuality under 

 extreme conditions. Taking the case of temperature, it has 

 been proved by experiment that the spores of a fungus 

 germinated after being exposed for two hours to air at a 

 temperature of 80° C. ( = 176° F.) ; germination or sprouting 

 of wheat and barley takes place at 5" C. ( = 41° F.), and 

 between these two extremes, various forms of life in an 

 active condition are to be met at every step. Cessation of 

 active function? in protoplasm usually cease when either of 

 the above extremes have been reached, but death does not 

 necessarily result ; when active life ceases, protoplasm often 

 possesses the power of entering a passive condition in which 

 it can remain until a favourable change in surroundings 

 enables it once more to assume the active condition. In 

 the passive condition protoplasm in many instances survives 

 exposure to greater extremes of temperature than those 



