314 THE STUDY OF PLANT COMMUNITIES • Chapter XI 



strong evidence of the present degree of climatic stability. Judg- 

 ment of such evidence must, of necessity, be tempered by what is 

 known of climatic cycles. In parts of the West, precipitation may 

 be several times as great during a period of sunspot minimum as 

 that during sunspot maximum. The condition of vegetation, par- 

 ticularly in relict communities, must be interpreted accordingly. 



GENERAL REFERENCES 



S. A. CAIN. Pollen Analysis as a Paleo-Ecological Research Method. 

 S. A. CAIN. Foundations of Plant Geography. 



F. E. CLEMENTS. The Relict Method in Dynamic Ecology. 



A. P DACKNOWSKI. Peat Deposits and Their Evidence of Climatic Change. 



G. ERDTMAN. An Introduction to Pollen Analysis. 



W S. Glock. Principles and Methods of Tree-Ring Analysis. 

 R B. SEARS. Climatic Interpretation of Postglacial Pollen Deposits in North 

 America. 



