34: 



THE PLANT LIFE OF MARYLAND 



which may accelerate or retard the effect of a given number of degrees 

 of total heat. 



Various attempts have been made to re-adjust phenological theory 

 to fit the facts, as for example, the proposal of Quetelet to take for 

 comparison the squares of the sums of temperatures, and that of von 

 Oettingen to consider the proper temperature for the starting point 

 for the addition of degrees to be that which gives results that best 

 serve to make observations on the plant concordant with theory. In 

 spite of the futility of the formal aim of phenology there is the high- 



Fig. 1. — Map of Maryland Showing Stations from which Climatological 

 Data Are Given. 



est importance to be attached to the duration of the growing season 

 for plants and to the character of the annual curve of temperature 

 both as respects the duration of the highest temperature of summer 

 and the lowness of the minimum temperatures of winter. 



It is only in a general study of the relations of temperature to the 

 character of the flora and the march of periodic phenomena in areas 

 of considerable size that any value attaches to the comparison of 

 annual or monthly means, seasonal or monthly mean maximum and 

 minimum or daily ranges. Owing to the geographical position of 

 Maryland and the increasing altitudes encountered in passing from 

 the coast to the westernmost county there are differences in the cli- 

 mate as respects temperature which are of importance to vegetation. 



