CONTENTS. 



I. Concept and History. 



The practical aspect . 

 The scientific aspect. 



HISTORICAL. 



Agricultural Indicators. 



Hilgard, 1860 5 



Chamberlin, 1877 5 



Merriam, 1898 6 



Hilgard, 1906 8 



Clements, 1910 9 



Shantz, 1911 10 



Kearney, Briggs, Shantz, McLane, and 



Piemeisel, 1914 11 



Shantz and Piemeisel, 1917 12 



Shantz and Aldous, 1917 13 



Weaver, 1919 13 



Forest Indicators. 



Cajander, 1909 14 



Clements, 1910 14 



Pearson, 1913-1914 15 



Zon, 1915 16 



Hole and Singh, 1916 16 



Korstian, 1917 17 



Grazing Indicators. 



Smith, 1899 19 



Bentley, 1902 20 



Griffiths, 1901, 1904, 1907, 1910, 1915.... 21 



Sampson, 1908, 1909, 1913, 1914 22 



Jardine, 1908, 1909, 1910, 1913 23 



Wooton, 1915, 1916 23 



Jardine and Hurtt, 1917 24 



Jardine and Anderson, 1919 24 



Sarvis, 1919 25 



Chresard and Water Requirement Studies. 



Significance 26 



The chresard 26 



Gain, 1895 26 



Kihlmann, 1890 27 



Briggs and Shantz, 1912 27 



The water requirement 28 



CONCEPT. 



General 28 



Animals as indicators 29 



Plant and community 29 



Sequences 30 



Direct and indirect sequences 31 



Direction of indication 32 



Scope 32 



Materials 33 



Basing studies 34 



PAGE. 



II. Bases and Criteria. 



BASES AND METHODS OF DETERMINATION. 



Fundamental relations 35 



The Physical Basis. 



Direct and indirect factors 36 



Controlling and limiting factors 36 



Climatic and edaphic factors 37 



Climates and habitats 38 



Variation of climate and habitat 39 



Inversion of factors 40 



Measurement of habitats 42 



The Physiological Basis. 



Kinds of response 43 



Effect of habit 43 



Individuality in response 44 



Effect of extreme conditions 44 



Phytometers 45 



The Associational Basis. 



Nature of association 47 



Dominants 47 



Equivalence of dominants 48 



Absence of dominants 49 



Subdominants 50 



Secondary species 51 



Plant and animal association 51 



The Successional Basis. 



Scope 51 



Sequence of indicators 52 



Major successions as indicators 53 



The Experimental Basis. 



Nature 53 



Essentials 54 



INDICATOR CRITERIA. 



Nature and kinds of criteria 55 



Species and genera 55 



Life-Forms. 



History 57 



Pound and Clements, 1S98-1900 57 



Raunkiaer, 1905 58 



Warming, 1908 59 



Drude, 1913 60 



Comparison of the systems 62 



Vegetation-forms 62 



Indicator significance of vegetation-form3 63 



Habitat-Forms. 



Concept and history 64 



Warming's system 64 



Modifications of Warming's system 65 



Indicator value 66 



Ecads 67 



I SI 3 J 



