MANUAL OP NATURE STUDY. Ill 



do trees give us of approach of winter ? (Full de- 

 velopment and coloration of buds, the coloration of 

 leaves whether frost comes or not.) What have 

 the leaves been doing all summer ? (Making food 

 for the plant.) What color is maintained during 

 the factory season? Green from chlorophyll. 

 This now becomes disorganized, and the food is 

 carried away by the sap to be stored up in buds for 

 next year's growth. This disarrangement, or 

 breaking up of the chlorophyll, is the cause of the 

 variety of color in the leaves. 



When winter is drawing nigh, the buds hurry 

 into winter quarters. To get ready for this change, 

 the buds make demand upon the plant for all the 

 supplies it can possibly furnish. It demands what 

 is already in the leaf and all the young bark can 

 spare. 



The sap begins immediately to make the trans- 

 fer. In fact, it has been doing a little of that work 

 all summer, for we know that the buds started to 

 build as soon as growing weather set in. But 

 now, along in September and October, the demand 

 from the buds has increased to such an extent that 

 the sap cannot furnish the leaf laboratory any 

 more material, so that the factory must "shut 

 down" and permit the food already made to be car- 

 ried away to build up the bud. 



Qolor^tion of leaves now begins, and as soon as 



