J-ANUART 16, 1920] 



SCIENCE 



67 



GENEEAL PEIOBLEMS 



I. Factors influencing the distribution of land 



plants and animals. 



(1) Geographic position. 



(2) Altitude. How far does altitude per sa 



influence distribution? 



(3) Topography. 



(a) Aspect, steepness of slope, valleys, 

 benches and other land forms. 



(6) Influence of size of land mass of 

 mountains, i. e., isolated moum- 

 tains vs. mountain masses. 



(c) Influence of water masses. 



(4) Historical factors. 



(a) Physical (geology, past climate). 

 (6) Biotic. 



(5) Climate. 



(a) Moisture. 

 (6) Temperature. 



(c) Solar radiation or insolaition. 



(d) Light. 



(e) Wind. 



(6) Soil. 



(a) Physical properties. 



1. Texture, desirability of a phys- 



ical constant: is wilting co- 

 efl3.cient such a constant? 



2. Soil moisture. 



3. Sou air. 



4. Soil temperature. 



5. Soil stratification or profile. 

 ( 6 ) Chemical properties. 



1. Solutions. 



(a) Aqueous extracts (cor- 

 relations with fertil- 

 ity. 



(&) Acid extracts. 



(c) Full analyses. 



2. Gases. Chemical properties of 



soU air. 

 (e) Biotic properties. All life plant as 

 well as animal, influencing the 

 soU. 



II. Factors influencing the distribution of aquatic 



plants and animals. 

 A. Standing water. 



(1) Geographic position. 



(2) Altitude. 



(3) Depth, and fluctuations of depth. 



(4) Historical factors. 



(a) Physical (geology, past cli- 



mate) . 



(b) Biotic. 



(5) Climate. 



(o) Temperature. 



(6) Solar radiation or insolation. 



(c) Light. 



(d) Wind. Important in aera- 



tion of water. 



(6) Wa/ter solution. 



(a) Color and turbidity. 



(6) Mineral and organic content. 



(c) Gaseous content. 



(7) Biotic factors. 



(8) Bottom. 

 B. Running water. 



(1) Geographic position. ' 



(2) Altitude. 



(3) Fluctuation. 



(a) Whether it fluctuates at all 

 (streams on east slope of 

 Cascade Mts. of Oregon do 

 not fluctuate). 



(6) Extent of fluctuation. 



(c) Period of fluctuation (di- 

 urnal or irregular). 



(4) Swiftness. 



(5) Depth. 



(6) Historical factors. 



(7) Climate. 



(a) Temperature. 

 (6) Solar radiation or in- 

 solation. 



(c) Light. 



(d) Wind. 



(8) Water solution. 



(o) Color and turbidity. 

 (6) Mineral and organic 

 content. 



(9) Biotic factors. 

 (10) Bottom. 



III. Studies of factors influencing distribution. 

 (A suggested method of procedure). 

 A. Field survey of the problem. 



(1) To determine significant associa- 



tions of plants and animals. 



(2) Determination of center and ex- 



tremes (northern and southern, 

 or east and west, or upper and 

 lower in altitude). 



(3) Instrumental readings at each of 



the above points, and their in- 

 terpretation. 

 B. Laboratory studies. 



(1) Growth under controlled condi- 



tions (with recording instru- 

 ments if possible). 



(2) Analysis of critical effects. 



