Flavone C-glycosides from seeds of Ziziphus jujuba var. spinosa Chemical Constituents from the Seeds of Ziziphus jujuba var. spinosa (Bunge) Hu Phenotypic variation in Ziziphus jujuba var. spinosa along a natural drought gradient Comparison on Characters of Leaf Anatomy of Ziziphus jujuba var.spinosa in Different Geography Environment