Wood is truly an amazing substance. Relatively light, very strong for its weight, elastic, capable of being shaped to an extraordinary degree. Why is wood so... woody?
Wood Handbook, FPL-GTR-113: Forest Products Laboratory. 1999. Wood handbook--Wood as an engineering material. Gen. Tech. Rep. FPL-GTR-113. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 463 p.
It seems clear that competition between plants has a bunch to do with it: whatever plants can get their leaves higher and wider spread has a big advantage in photosynthesis and thus in fitness. It seems pretty clear that wind has a bunch to do with it: wind can put great stresses on plants--especially those that reach high and are widely spread.
But I really do wish that by now somebody had told me why wood is so... woody.
Tomorrow: I also wish someone would tell me why doping iron with carbon atoms changes its properties so much...