Chapter XII 



CYTOST IN THE PLANT WORLD 



In the preface the writer has drawn attention to his 

 earliest experiments with plants, conducted over forty 

 years ago. At that time nothing was known of the 

 role of cytost in animal physiology. In view of the 

 experiments with animals it is interesting to recall 

 these early experiments, for, curiously enough, they 

 are capable of interpretation from the standpoint of 

 the cytost hypothesis. 



For many years it has been generally recognized 

 that plants cannot be grown in the same soil for an 

 indefinite succession of years, a fact commonly ex- 

 pressed in the agriculturists' "law of the minimum," 

 which states that as soon as the concentration of cer- 

 tain elements in the soil has reached a minimum level, 

 plants are unable to withdraw those elements in a 

 quantity sufficient to permit growth. If, however, 

 such elements are added to the soil, normal growth of 

 the plants ensues. This is the essence of the well- 

 known effect of commercial fertilizers on plant 

 growth. 



In the author's experiments referred to above it was 

 observed that upon the addition of rich virgin soil 

 to exhausted earth, healthy growth of transplanted 



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