1.Using a simple variation-fitting method，the exciton binding energies of a sawtooth-shaped quantum well are calculated as a function of an electric field，and the explanation of the results is also given.
2.As a result, on the inner wall of the ray tracheid has sawtooth thickening obviously. The pit of cross field is windows and pine shape. The ratio of the tracheid length to width is about 50. Average air dry density is about 598kg/m 3. The shrinkage of difference is about 1 8;
