Exo-glycosidases Activities in Artemisia sphaerocephalaMucilaginous Achene Germination Process Seed Germination in Artemisia sphaerocephala I. the Structure and Function of the Mucilaginous Achene Exo-glycosidases Activities in Artemisia sphaerocephala Mucilaginous Achene Germination Process Comparison of Germination Strategies of Artemisia ordosica with Its Two Congeners from Deserts of China and Israel