FACTORS AFFECTING SEASONAL ACTIVITIES. 13 



centigrade-hour-unit represented in such amounts is 9/1600, 

 and of Fahrenheit-hour-units 81/8000. The number of hour 

 units is therefore to be found by simple division, -f- indicates 

 temperature exposures above freezing; below freezing. 



THKRMOGRAPHIC OBSERVATIONS IN N. Y. EOT. GARDEN, IQOO-OI 



