Four kinds of Eucalyptus wood have been observed with the scanning electron microscope.The ultrastructure of pits and warly layers on the cell wall of vessel, fiber and tracheid of the four kinds of wood have been analysed. The findings are as follows.The four kinds of Eucalyptus wood are rich in tylosis, which blocks the intervessel axial passway,and partly covers the intervasscular pits and vessel-ray pits, thus greatly influencing the permeability.These are the main causes leading to the drying collapse.With heat treatment,the drying collapes of E.viminalis and E.tereticornis can be relieve...
