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 4o 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 be 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 in 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 
