Cytoembryological Studies on Apomixis in Boehmeria silvestrii Ultrastructure of Megasprogenesis in Faculative Apomictic Monosonic Addition Line M14  of Beta corolliflora of Sugar Beet Megasporogenesis and Development of Female Gametophyte in the Apomictic Monosomic Addition Line M14 of Beta corolliflora in Sugar Beet ISSR analysis of genetic diversity of germplasm resources of Bothriochloa ischaemum in Shanxi Apomixis and Embryo Cell Development for Two Main-plant Early Bearing Varieties of Walnut in Xinjiang Characteristics of Obligate Apomixis in Dandelion (Taraxacum antungense)