PALEOBOTANY BERRY. 373 



plant life on the earth the period of preserved records may be ap- 

 proached through a long antecedent vista of theoretic and more or 

 less speculative conclusions, which, since plant life seems to have 

 preceded the first distinctive animal life, reach back to the hypotheti- 

 cal origin of life itself. These stages may be somewhat arbitrarily 

 considered as embracing first an Eophytic stage, followed by a 

 Chlorophyllic stage, and the latter may be divided into an Algal 

 substage, and a second or Pteridophytic substage comprising the 

 origin and subsequent evolution of land plants. 



The more important advances during the evolution of land plants 

 have been the acquisition of secondary wood formation and the 

 development of heterospory and the seed habit. 



The marvelous recent discoveries in bacteriology have shown by 

 what means the first life forms derived their nourishment through 

 the utilization of inorganic materials. Bacteria are the simplest as 

 well as the smallest of known organisms, and because of their minute 

 size and similarities in form they are classified largely by the pro- 

 found chemical reactions which they inaugurate. It is quite possible 

 that they represent the first stage in the evolution of life upon the 

 globe. At any rate they illustrate for us the manner in which, in a 

 prechlorophyllic stage of plant history, simple organisms like bacteria 

 derive their nitrogen from ammonia compounds and their energy by 

 means of oxidizing catalyzers. All organisms which do not utilize 

 organic carbon must have some source of energy that will enable 

 them to take up carbon dioxide and partially replace the oxygen 

 with hydrogen and thus build up complex organic compounds. The 

 energy for this transformation is obcained b} T the oxidation of carbon, 

 nitrogen, sulphur, or iron derived from hydrogen sulphide, ammonia, 

 etc. These forms constitute the four primitive types of oxidizing 

 bacteria that are known at the present time, and such forms which re- 

 quire no organic food materials are termed Prototrophic bacteria 

 (nitrifying, nitrogen fixing, sulphur and iron oxidizing). Thus his- 

 torically chemosynthesis must have preceded photosynthesis. Recent 

 studies show that some form of photosynthesis by means of which cer- 

 tain bacteria utilize purple and other pigments in employing the 

 infra-red rays of light probably preceded and may have been a step 

 toward chlorophyll activities. The primitive bacteria have a proteid 

 cell Avail which is a modification of the general protoplasm, and not 

 one of cellulose ; they contain chromatin but do not organize a definite 

 nucleus, and they multiply largely by vegetative fission. Systematists 

 erect a phylum, the Schizophyta, to which they refer the Schizomy- 

 cetes or bacteria, and the Cyanophyceae or the so-called blue-green 

 algae. The latter are microscopic forms with a related organization, 

 formerly considered as the ancestors of the bacteria, which were thus 

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