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White pine

 Normally because of lack of light.  Without light, buds do not open.  When buds die there are no leaves or needles, and the cambium (growing part of the branch) along the branch also dies.  Other reasons for the death of branches are breaking by storms and attacks by fungi or insects. 

Why do lower branches of trees gradually die?

 

How is charcoal made?
Wood supplied with plenty of air burns freely. If deprived of air it gives off gas and turns to charcoal.  Charcoal can be made simply by stacking wood together, covering with earth, lighting in several places, and maintaining a slow burn by letting in small amounts of air.  When the temperature reaches 500� F a chemical reaction occurs which makes it very hot, reduces the air to a minimum, and turns the wood to carbon (charcoal).  The charring process takes a few day or a couple weeks, according to the size of the wood pile.  This includes time for slow cooling to a point when the charcoal can be exposed to the air and removed without bursting into flame.  

Charcoal

 

What is the oldest known tree food used by man? 

 Walnuts.  Shells of walnuts were found in the Swiss Lake dwellings of Neolithic man, dating from about 7000 B.C.  They were found with his bones and the bones of the animals he snared for food.  These were the Persian-walnut type, Juglans regia, which we call English walnuts because they were first brought to America by the English settlers of Virginia. 

Walnuts

 

What tree does silk come from?

Silkworms

The white mulberry tree Morus alba, is responsible for silk, but unlike the kapok tree it does not produce the threads by itself.  First a caterpillar larva of the silk moth, Bombyx mori, must eat the leaves and mix the mash with chemicals from its glands.  Then it squeezes out the mixture through tiny nozzles in its' mouth.  The silk strand hardens when touched by air to form silvery threads.  The caterpillar of the silkworm makes these thread to build itself a cocoon, into which to pupate and turn into a moth. 

 

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