Abstract:The yellow green hard callus is the best embryogenic callus, which obtained from the stem tip of Populus alba×(P.davidiana×P.simonii)×P.tomentosa on the induced medium (MS+KT0.1mg\·L-1+2,4D 0.05mg\·L-1) after 10 days culture. Its formation frequeny of adventure buds, adventure roots and somatic embryos ane 100%、19.4% and 13.3% respectively on the differentiated medium (MS+KT 0.3mg\·L-1). Organs and somatic embryos are all derived from the surface layer of calli. The somatic embryogenesis is very similar with the zygote embryogenesis. The esterase isozymes and soluble protein bands of various calli are very different.