MANUAL OF NATURF 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. 
Coloration of leaves now begins, and as soon as 
