20 TREES 



the soil. The abundant lime in dead leaves is active in the 

 formation of humus, which is decayed vegetable matter. 

 We call it "leaf mould.'* So even the waste portions have 

 their effectual work to do for the tree's good. 



The leaves of certain trees in regions of mild winters per- 

 sist until tiiey are pushed off by the swelling buds in spring. 

 Others cling a year longer, in sorry contrast with the new 

 foliage. Yve may believe that this is an indolent habit in- 

 duced by climatic conditions. 



Leaves of evergreens cling from three to five years. 

 Families and individuals differ; altitude and latitude pro- 

 duce variations. An evergreen in winter is a dull-looking 

 object, if we could compare it with its summer foliage. Its 

 chlorophyll granules withdraw from the surface of the leaf. 



They seek the lower ends of the palisade cells, as far as 

 they can get from the leaf surface, assume a dull reddish 

 brown or brownish yellow color, huddle in clumps, their 

 water content greatly reduced, and thus hibernate, much as 

 the cells of the cambium are doing under the bark. In 

 this condition, alternate freezing and thawing seem to do 

 no harm, and the leaves are ready in spring to resume the 

 starch-making function if they are still young. Naturally, 

 the oldest leaves are least capable of this work, and least is 

 expected of them. Gradually they die and drop as new 

 ones come on. As among broad-leaved trees, the zone of 

 foliage in evergreens is an outer dome of newest shoots ; the 

 framework of large limbs is practically destitute of leaves. 



How Trees Spend the Winter 



Nine out of every ten intelligent people will see nothing 

 of interest in a row of bare trees. They casually state that 

 buds are made in the early spring. They miss seeing the 



