202 HIGHER PLANTS AND SOIL MICROORGANISMS 



nitrogen; (4) assimilation by plants of such organic compounds as 

 amino acids or lower carbohydrates which may be produced by 

 microorganisms as incompletely decomposed products or syn- 

 thetic products; (5) associative development in such special cases 

 as algae and bacteria, or fungi and algae. 



There may be actual penetration of the roots in certain 

 instances. Some invasions of the microbes result injuriously; 

 such effects are produced by the numerous plant pathogens which 

 inhabit the soil. The invasion of symbiotic agents, as the legume 

 associates and certain mycorrhiza fungi, produces very evident 

 beneficial results. 



LITERATURE 



L LinsTDEGARDH, H. Def Kreislaiif der Kohlensaure in der Natur. 308 pages. 

 Gustav Fischer. Jena, 1924. 



2. Rayner, M. C. Mycorrhiza. An account of non-pathogenic infection by 



fungi in vascular plants and Bryophytes. New Phytologist Reprint, 

 No. 15. 246 pages. Wheldon & Wesley, Ltd. London, 1927. 



3. Starkey, R. L. Some influences of the development of higher plants 



upon the microorganisms in the soil. Soil Science, 27, 1929: 319-334; 

 355-378; 433-444. 



4. Waksman, S. a. Principles of soil microbiology. Chapters 11 and 29. 



The Williams & Wilkins Co. Baltimore, 1927. 



