RELATION OF LEAF STRUCTURE TO PHYSICAL FACTORS 



2 9 



number of situations and altitudes. The figures in the table indi- 

 cate the average extremes for the season. 



TEMPERATURE. Continuous automatic records of temperature 

 were made during fifteen weeks of 1903 for the foothills (2000 

 meters), the subalpine region (2600 m.), and the alpine region 

 (3800 m.). Similar records were made during eight weeks of 

 1904 in the foothills, and in the spruce forest and gravel slide 

 formations of the subalpine region. Readings for the brook bank 

 and half gravel formations of the subalpine region were made twice 

 daily during 1904. Frequent single readings of soil, air and sur- 

 face of ground were made during the two summers throughout the 

 three regions. The air temperatures in the table are the average of 

 the daily extremes for the growing season. The ground and soil 

 temperatures are the average of the single readings. All tempera- 

 ture readings are expressed in Fahrenheit degrees. 



TABLE OF PHYSICAL FACTORS 



IV. TYPIFICATION OF ENDEMIC SPECIES 



The plants studied in relation to their leaf structure and habitat 

 comprise about three hundred species collected in the Colorado foot- 

 hills and mountains of the Pike's Peak region of the Rocky Moun- 



