18 THE WEATHER 



1. To determine the general oncoming of spring. 



2. To determine the fitful or varialjle features of spring. 



3. To determine the epoch of the full activity of the advancing 

 season. 



4. To determine the active physiological epoch of the year. 



5. To determine the maturation of the season. 



6. To determine the oncoming of the decline of fall. 



7. To determine the approach of winter. 



8. To determine the features of the winter epoch. 



9. To determine the fleeting or fugitive epochs of the year. 



Good phenological observations upon plants should satisfy the fol- 

 lowing tests, as given by Hoffmann : — 



1. They should represent as broad a distribution as possible of the 

 given species, selected for observation. 



2. Ease and certainty of identifying the definite phases which are 

 to be observed. 



3. The utility of the observations as regards biological questions, 

 such as the vegetative periods, time of ripening, etc. 



4. Representation of the entire vegetation period. 



5. Consideration of those species which are found in almost all 

 published observations, and especially of those whose development is 

 not influenced by momentary or accidental circumstances, as is the 

 dandelion. 



The epochs of vegetation that should be observed for most pheno- 

 logical purposes are these: — 



1. Upper surface of the leaf first visible or spread open. 



2. First blossoms open. 



3. First fruit ripe. 



4. All leaves, or more than half of them, colored. 



Typical and average plants should always be selected for observa- 

 tion, and they should be few in number. A dozen well-selected species 

 will afford more satisfactory records year by year than observations 

 made at random upon a great variety of plants. For the sudden moods 

 of spring, the peach and dandelion are useful for observation, but such 

 plants — those which respond quickly to every fitful variation of the 



