Microsporogenesis and Variation in Pollen Size of Populus×xiaozhuanica ‘Baicheng-2’ Colchicine-induced Pollen Chromosome Doubling and its Cytological Effects in Populus alba L. Genetical Studies on Progenies of Somatic Hybrids between Brassica napus and Descurainia sophia Meiosis and Chromosome Behavior of Microsporocytes in Populus adenopoda Maxim Meiotic Chromosome Behavior of Pollen Mother Cells and Gamete Fertility in Triploid Grape ‘Summer Black’ A cytogenetic study of five species in the genus Osmunda Chromosome Behavior of Pollen Mother Cell Meiosis in the Hybrid Progenies from Triticum timopheevi×Avena fatua L.var.glabrata Pat