94 THE HABITAT 



THE EXPRESSION OF PHYSICAL FACTOR RESULTS 



137. The form of results. It is almost inevitable that the general adop- 

 tion of precise methods of measuring the habitat will result in a common 

 form for expressing the physical character of the latter. An actual diag- 

 nosis of each habitat is not a difficult matter, after the factors are carefully 

 measured, and will unquestionably lead to very desirable definiteness and 

 precision. The accurate investigation of the physical factors of a number 

 of habitats for one growing season furnishes the necessary material for a 

 diagnosis based upon the mean for the growing season. Similar results for 

 two or three seasons will yield a diagnosis as accurate and as final as that 

 of a formation, or, indeed, as that of many species. The author's investi- 

 gations have not yet gone far enough to warrant proposing a final form for 

 this, but the following diagnosis is offered as a suggestion : 



Elymus-Muhlenbergia-chalicium. Habitat: holard 9 per cent, chresard 8 

 per cent, relative humidity 40 per cent, light 0.6, soil colluvial gravel (gravel 

 70 per cent, sand 27 per cent, silt 3 per cent), air temperature 65, surface 

 82, soil 59, wind 10 miles, rainfall 8 inches, altitude 2,800 m., slope 23, 

 exposure south, surface even, cover open, no active biotic agencies. 



The detailed comparison of habitats is made most readily by the graphic 

 method of curves, which constitute the most desirable form of expression in 

 connection with the original record upon which they are based. Factor 

 means are particularly desirable for diagnostic purposes, and they furnish 

 valuable curves also. Factor sums are impracticable at present, and it seems 

 doubtful that they will ever he of much value. It is by no means impos- 

 sible, however, that a more detailed and exact knowledge of the physiology 

 of adaptation, coupled with methods of precision in the habitat, will render 

 them necessary. 



Factor Records 



138. Experience has shown that the practice of making hasty and often 

 formless records in the field is unwise and is apt to be inaccurate as well. The 

 time saved m the field is more than counterbalanced by that consumed in 

 copying the results into the permanent form. The danger of error in field 

 notes rapidly taken is very grave, and the chance of confusion and the waste 

 of time in deciphering them are great. Moreover, the task of checking a 

 copy with the original, which is absolutely necessary for accuracy, involves 

 a further expenditure of time and energy-. For these reasons the field record 

 should be made in permanent form. Definite record sheets are used, and 

 the invariable rule is made that all readings are to be noted in ink at the 

 time and spot where they are taken. On a long journey, or in the face of 



