CLIMATIC CONDITIONS OF THE UNITED STATES. 381 



employing either political designations (as the names of States), 

 physiographical ones (such as rivers and mountain ranges), or the 

 geographical ones of latitude and longitude. It is not to be implied 

 that the different and separated portions of any climatic province, as 

 these provinces are here characterized, have the same climatic condi- 

 tions in general. The chart under consideration has been derived 

 from moisture and temperature indices of certain specific kinds, 

 obtained in certain specified ways, and the separate portions of the 

 same province are to be considered as alike only with reference to the 

 ranges of the indices employed. If other climatic indices were used 

 these areas might not appear alike. It is obvious, for example, that 

 other climatic conditions than those actually represented by the chart 

 of figure 19 render the northwestern portion of the very cool humid 

 province decidedly different climatically from the northeastern portion 

 of the same province. 



VI. GENERAL CONCLUSIONS FROM STUDY OF CLIMATIC 

 CONDITIONS IN THE UNITED STATES. 



The climatic conditions considered in the preceding sections are 

 mainly those of temperature and moisture. These are surely the most 

 generally important climatic conditions met with in the natural con- 

 trol of plant distribution, and they are also the ones for which the best 

 data are available, although the data for temperature conditions are 

 much more satisfactory than those for moisture conditions. It is also 

 true that methods for interpreting temperature observations are con- 

 siderably farther advanced than are those for interpreting observations 

 on the moisture conditions; methods by which temperature values 

 may be weighted and integrated are available (though it must not be 

 forgotten that these methods are susceptible of great improvement), 

 but no general system for weighting moisture conditions has yet been 

 suggested. The studies here repoted all lead unmistakably to the 

 conviction that climatological methods and climatological interpre- 

 tation, as so far developed, are wofuUy inadequate for the solution of 

 problems deahng with the control of plant distribution. From the 

 standpoint of ecology and agriculture no great progress is to be expected 

 until much more attention is given to the devising of new methods for 

 obtaining the climatic records and new methods for interpreting these 

 records, and until a new point of view is reached, different in many 

 respects from that hitherto held by workers in climatology. It can 

 not be too strongly emphasized that the whole field of ecological 

 climatology first requires original research in these fundamental and 

 primary lines, research of an originality pronounced enough to be able 

 to set aside many of the now stereotyped methods of observation and 

 interpretation employed in chmatology and meteorology, and it is to 

 be hoped that those entering this new field of scientific endeavor will 



