1．The samples of polyethylene irradiated with 1，20，50，1 00，and 200 megarad γ一ray were crystallized from dilute xylene solutions under the same conditions．The mot-phology of a series of crystals obtained changes regularly as the dose increases．Below the gel point

single crystals could be obtained． Beyond this point，dendritic crystals (becoming more and more irregular with increasing dose) were obtained．But when the crystallizing temperature was lowered or the cooling rate Was decreased，regular dendritic crystals or even single crystals could again be obtained．Therefore this change of morphology with increasing dose is due not to the change of the structure of the mole-cules，but to the increasing of the degree of supersatu．ration during crystallization．The higher the gel fraction is，the higher is the degree of supersaturation．2．Three kinds of typical crystalline morphology(they belong tO the linear，bran-ched，and three-dimensional network molecules) were observed from irradiated poly-ethylene．This indicates that within suitable range of dose．these three kinds of mole-cules do exist in irradiated polyethylene at the same time．3． The crystallization process of the polymer from dilute solution is also a process of spontaneous separation of the unlike molecules and a process of congregation of the like molecules．4． Single crystals of polyethylene prepared under the same conditions had been ir-radiated separately with 5，20，50，100，and 200 megarad γ-ray．The morphology of these irradiated crystals was studied with an electron microscope

Some of them re-mained unchanged，but．there were Iots of wrinkles on the others．Moreover，even in the same single crystal，many wrinkles were found in some sectors，but none in the others． The unequal distribution of the wrinkles indicates that a perfect crystal lattice has higher resistance to γ-radiation．It also indicates that every sector in a hollow pyramid crystal is a structural unit of more perfect crystalline lattice．