EXCESS OF NUTRIMENT. 133 



cording to the observations of M. Heyer, the starch 

 thus deposited in the body of the tree can be recog- 

 nised in its known form by the aid of a good micro- 

 scope. The barks of several aspens and pine-trees * 

 contain so much of this substance, that it can be 

 extracted from them as from potatoes by trituration 

 with water. It exists also in the roots and other 

 parts of perennial plants. A very early winter, or 

 sudden change of temperature, prevents the forma- 

 tion of this provision for the following year ; the 

 wood, as in the case of the vine-stock, does not 

 ripen, and its growth is in the next year very 

 limited. 



From the starch thus accumulated, sugar and gum 

 are produced in the succeeding spring, while from 

 the gum those constituents of the leaves and young 

 sprouts which contain no nitrogen are in their turn 

 formed. After potatoes have germinated, the quantity 

 of starch in them is found diminished. The juice of 

 the maple-tree ceases to be sweet from the loss of its 

 sugar when its buds, blossoms, and leaves attain 

 their maturity. 



The branch of a willow, which contains a large 

 quantity of granules of starch in every part of its 

 woody substance, puts forth both roots and leaves 

 in pure distilled rain-water; but in proportion as it 



* It is well known that bread is made from the bark of pines in 

 Sweden during famines. 



The following directions are given by Professor Autenrieth for pre- 

 paring a palatable and nutritious bread from the heech and other woods 

 destitute of turpentine. Every thing soluble in water is first removed 

 by frequent maceration and boiling, the wood is then to be reduced to 

 a minute state of division, not merely into fine fibres, but actual pow- 

 der ; and after being repeatedly subjected to heat in an oven, is ground 

 in the usual manner of corn. Wood thus prepared, according to the 

 author, acquires the smell and taste of corn flour. It is, however, 

 never quite white. It agrees with corn flour in not fermenting with- 

 out the addition of leaven, and in this case some leaven of corn flour is 

 found to answer best. With this it makes a perfectly uniform and 

 spongy bread ; and when it is thoroughly baked, and has much crust, 

 it has a much better taste of bread than what in time of scarcity is pre- 

 pared from the bran and husks of corn. Wood-flour also, boiled in 

 water, forms a thick, tough, trembling jelly, which is very nutritious.. 

 — Philosophical Transactions y 1827. 



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