206 UNDER THE OPEN SKY 



plant has quite enough for its present pur- 

 poses, so it is not carried away. Now the 

 leaves, thin and dry, as compared with their 

 summer condition, are cast aside, thus re- 

 turning to the soil the minerals that had 

 been taken up, and which now are in good 

 shape to be used over again. This is the 

 reason why woods earth is so good a soil 

 for potted plants: it is full of concentrated 

 nourishment from the decayed leaves. As 

 before hinted, the leaves may become a 

 source of positive danger to the tree. They 

 have such broad surfaces that the heavy 

 winter winds could catch firm hold of them 

 and thus break off branches, or even uproot 

 the trees. These same leaves would be 

 likely to catch and hold the snow, and thus 

 would be again more than the tree could 

 possibly bear. 



So after all its lifework has been com- 

 pleted, with a gentle consideration for the 

 tree that bore it, the leaf gently draws 

 through the base of its own stem a sheet of 

 cork, dressing the wound, so as to prevent 

 infection even before the wound is made. 



