Morphology and intermittent germination characteristics of two types of synaptospermy: a case study of Tribulus terrester and Marrubium vulgare Germination characteristics and ecological adaptation of dimorphic seeds of Borszczowia aralocaspica Fruit-set patterns and burial mechanism for subterranean dispersal units of Ceratocarpus arenarius Seed Dispersal and Germination of an Endangered and Rare Species Urophysa rockii (Ranunculaceae)