250 COMPENDIUM OF GENERAL BOTANY. 



stimuli, the behavior of idioplasm). His logical mind, however, 

 finally led him to that substance whose mechanism we cannot 

 understand, but which science has long considered as the sustainer of 

 the various life-phenomena, namely, plasm. In this substance we 

 also believe the forces to be concentrated which enter into the phe- 

 nomena of life and growth. 



With idioplasm, the structure and mechanism of which Nageli 

 considers the "greatest mystery in the doctrine of descent," we also 

 associate the miracle of creation ; we know that " living plasm " 

 is necessary for the existence of a living cell, and hence for every 

 living plant. "Mystery" and "miracle" are the two contrasting 

 terms. Let our opponents not be misled : idealist and materialist 

 both fail to comprehend the natural causes of certain things. The 

 idealist knows from experience that the thorough investigation of 

 any phenomenon in nature will sooner or later meet with conditions 

 which must be looked upon as given. The materialist ignores this 

 experience, does not explain the " mystery," but still maintains that 

 the ultimate causes are capable of a natural explanation without 

 miraculous intervention. Is it not well for the human mind, 

 which is only a breath of the creative Spirit, to recognize one's 

 Creator in nature ? Is it, then, intellectual weakness to acknowl- 

 edge the Almighty ? Why did Nageli write, " To deny spontaneous 

 generation is to declare the miracle"? Although we declare the 

 miracle, we are stricter empiricists than our opponents; we also 

 value scientific investigations which bring to light truths which the 

 human intellect can arrive only at after much toil. 



APPENDIX. 



The Life-period of Plants. 



1. The Schizomycetes live about 3-J hours on the average, after 

 which the individual divides(NAGELi and SCHWENDENEE). 



2. Moulds and microscopic algse live from several days to sev- 

 eral months. 



3. Many plants live one or two, more rarely several, " vegetative 

 periods," which vegetative period may extend over a period of from 

 J to f of a year. Winter in the temperate zones and the dry period 

 in hot climates is the time of vegetative rest or seed -rest. Accord- 

 ingly we speak of annual, biennial, or perennial plants (see p. 158). 



