132 NATURAL HISTORY OP THE FARM 



Optional Study 4. Autumnal Coloration and Leaf Fall 



Probably the grandest phenomenon of nature that is pecu- 

 liar to our northern latitude, is the coloration of the woods 

 in autumn. All marvel at the display. Few observe it 

 carefully. It is the object of this study to direct attention to 

 some of the external features of it : the mechanical prepara- 

 tion of the leaf for its fall, the changing pigments of the 

 residual leaf contents, and the relation of these changes to 

 temperature and rainfall, etc. The whole process is a 

 wonderful adaptation to meet winter conditions, and how 

 admirably nature manages it! She first withdraws all food 

 materials from the leaves into the stem and branches. Then 

 she starts her wonderful display by elaborating bright pig- 

 ments out of the residue. Then she casts the leaves off in 

 an orderly fashion, developing breaking points at proper 

 places. So she diminishes to a very small percentage the 

 area of exposed evaporating surfaces, and thus she conserves 

 moisture in the plant body through the long cold season. 

 The changing hues of autumn are more or less accidental by- 

 products of this process; but they are very beautiful. 



The work of this study should include serial observations 

 on a dozen or more of the more brilliantly colored species, 

 continued from the first appearance of an autumn tint until 

 the last of the leaves have fallen. The same trees should be 

 observed day by day, account being taken of the relevant 

 weather conditions. Hence, trees, shrubs and vines near at 

 hand should be chosen. Those on the lawn are apt to be as 

 good as any, since ornamental planting in our day takes 

 careful forethought for the autumnal display. 



