OCTOBER 205 



the young twigs. In these the food is pre- 

 pared that builds up all the rest of the plant. 

 This work can be done well only where the 

 sunlight is fairly strong. 



As the days get shorter and the sun shines 

 more slantwise, there is not heat enough for 

 good growth, so our trees prepare to " close 

 up shop" for the winter. When, they come 

 to do this, they find themselves with two 

 sorts of material in their leaves, the live 

 material, that did the work and is still good, 

 — protoplasm the scientist calls it, — and a 

 lot of by-product in the shape of mirieral 

 matter brought up from the soil. The 

 protoplasm can be taken apart, carried back 

 into the trunk, and stored away for use next 

 year. It is getting too cold for the plant to 

 do this well, so it puts "warming up" cur- 

 tains at the windows, — that is, it colors 

 its leaves yellow or red, and thus absorbs 

 the sun's rays and furnishes warmth enough 

 to permit the plant to carry the living sub- 

 stance out of the leaves into the trunk or 

 the roots. 



Of the mineral matter in the leaves the 



