THE AMERICAN BOTANIST. 



31 



From the point of view of the naturalist, the ideal crite- 

 rion of the advance of spring must be the awakening of 

 plant life. Plants are fixed in their habitat, and are sub- 

 jected to all the influences of their environment, and while 

 the progress of growth is largely controlled by chemical 

 and physical features of the soil, the chief factors must be 

 temperature, moisture, and sunshine. Plants reflect per- 

 fectly the successive phrases of the grand panorama of the 

 seasons from the moment when the first warm breath per- 

 suades the crocus to push up its flowers through the snow\ 

 The determination of the commencement of the various 

 phenoma of plant life, of the unfolding of the foliage and 

 flower, the ripening of the fruit, and fall of the leaf, in their 

 relation to the seasonal changes that take place, consti- 

 tute the so-called phenological observations. Phenolog\" 

 is extremely important in the study of the geography of 

 plants, and is of no less value for climatology, though 

 meteorologists have rather neglected this attractive work. 

 The large mass of material available must generally be 

 sought in botanical works, and it is to be regretted that 

 the memoir on the subject of phenology prepared by Prof. 

 Cleveland Abbe in 1891 was not published by the Weather 

 Bureau. 



The diflerence in the behavior of different species of 

 plants serves to give account of the gradual advance of 

 spring. Thus the snowdrop, bloodroot, and claytonia 

 herald the earliest touch of spring ; peaches and cherries 

 bloom early, and often suffer for their intrepidity ; while 

 oaks and walnuts are slow to respond to the influence of 

 warm weather. There are two ways of utilizing the ma- 

 terial furnished by phenological observations. By com- 

 paring the dates of blossoming of the same species of plant 

 at different places, the retardation of vegetative develop- 

 ment with increasing latitude is brought out, with such 

 variations as may be caused by topographical features. 

 Using the island of Lesina in the Adriatic Sea (latitude 43° 

 N.) as the starting point, it has been found that spring at 

 Paris (latitude 48°) is retarded forty-three days, at Brus- 



