VALUE OF FRUIT AS FOOD 269 



and perfumes, which have become indispensable in art, manufacture, and 

 medicine. 



The leaves take charge of the nourishment of the tree as soon 

 as they open. They prepare food only in the day time and in the pres- 

 ence of the sunlight; the more warmth the more work. They make a 

 complex substance known as starch, containing carbon, oxygen, and 

 hydrogen. The tree finds its growing season inaugurated when it is 

 supplied with foliage. Each leaf is a builder. A large sugar maple is 

 estimated to have 432,000 leaves, presenting to the sunlight an area of 

 half an acre. 



The closing of the leaflets at night reduces evaporation, which is a 

 cooling process, and enables the tree to save much of its heat. The 

 cause of the brilliant foliage in the autumn is the chemical decomposition 

 of the useless mineral substance in the leaves when the living substance 

 is withdrawn. No two of the untold millions of leaves in the forest 

 are exactly alike. 



The wood of the tree is not alive, neither is the bark. But between 

 the bark and the wood is a peculiar cellular substance known as cam- 

 bium, which is the living part of the tree, from which new tissues are 

 developed. This ministry, by the leaves, is what lengthens the branches 

 and roots and adds to the tree's diameter. The upward mounting of the 

 sap remains one of the unexplored mysteries of plant life. If a tree is 

 girdled it usually dies because the descending sap can not reach the 

 roots, which soon perish of starvation from lack of food sent them by 

 the leaves. 



A tree does not die of old age. It accumulates infirmities with the 

 years and has many diseases. It may starve or die of thirst; caterpillars 

 may eat its foliage, scale bugs suck its juices, beetles tunnel under the 

 bark, scab, rust, moulds, rot, blight, may prey upon it. The wind is 

 also an enemy. Peeling the bark of the birch does not kill it. The lum- 

 bering season is over when the sap begins to stream upward, as wood 

 cut "in the sap" is liable to decay. A sugar maple in three weeks yields 

 of its life blood to the extent of twenty-five gallons (seventy drops falling 

 every minute), which boils down to a little less than five pounds of 

 sugar. The trees are not injured if properly treated, but exhausted by 

 being bored too much or at the wrong time. 



VALUE OF FRUIT AS FOOD. ' 



Written for Green's Fruit Grower by Robert Sparks Walker. 



This is both a scientific and practical subject. It is one that de- 

 serves careful consideration. Every one should know just how much 

 of the various constituents of food that fruit contains. The various con- 

 stituents of foods are grouped under four heads. They are: Carbohy- 

 drates, fat, protein, and ash. 



The human body requires a certain amount of pure water daily. The 



