Comparative Studies on Structural Feature of Vessels of Four Genera of Cycads with Angiosperm

The tissues of leaf of Cycas taiwaniana,Bowenia serrulata and Dioon eduleand tissue of root of Macrozamia longispina of cycads,and leaves of Michelia alba and Amygdalus persicaof angiosperm were observed by scanning electron microscope.The results showed that there are many types of vessels in four genera of two families of cycads,the manner and process of development and constitution in structural characteristics of vessel of cycads and angiosperm are identical,some characters of vessel such as inclined extent of perforation plate of end wall etc.showed that some angiosperm are more primitive then that of cycads.In vessels of species of angiosperm,many are band shape,and without end wall,only have two lateral walls and another two narrow margins,the top is acute or with an arc margin,many perforations located in lateral wall.Cognized to vessel of cycads,help us to understand the mechanism which these most primitive seed plants extant how to adapted to harsh environments and their evolutionary level,and has significance to use efficiency measure protect these rarity plants and has significance to plant anatomy,plant systematics and plant evolution.