冠果草的花部发育——兼论冠果草与近缘属的亲缘关系

利用扫描电镜首次对冠果草（Ｓａｇｉｔｔａｒｉａｇｕａｙａｎｅｎｓｉｓ，Ｈ．Ｂ．Ｋ．ｓｓｐ．ｌａｐｐｕｌａ（Ｄ．Ｄｏｎ）Ｄｏｇｉｎ）的花器官发生进行了观察，结果显示：萼片原基以螺旋状方式向心发生，花瓣原基以接近轮状方式近同时发生，并与萼片原基因相间交替排列，不存在花瓣－雄蕊复合原基；最外轮６枚雄蕊原基的发生与萼片原基和花瓣原基相交替，并倾向于两两对萼的形式发生，对萼雄蕊对和瓣雄蕊的对仅仅是这种相间交

FLORAL ORGANOGENESIS OF SAGITTARIA GUAYANENSIS SSP.LAPPUL A--WITH ADDITIONAL REFERENCE TO ITS RELATIONSHIP WITH THE RELATIVE GENERA

Floraldevelopm ent of Sagittaria guayanensis H.B.K.ssp.lappula(D.Don)Bogin (Alism a- taceae)has been observed under scanning electron m icroscope(SEM).The sepalprim ordia firstinitiates on radiispirally,and a w hirlofthree alternisepalous petalprim ordia form nearly sim ultaneously.Deve- lopm entalstudies confirm thattheexistenceofpetal-stam en com plex prim ordia isafalse appearanceand do not support that antipetalous stam en pairs are generalcharacteristics offloralconstructure in Alis- m ataceae. Itshows that the first six stam en prim ordia locate at the sites alternate w ith the sepalpri- m ordium and the petalprim ordium ,and they are m ore like antisepalous,w hereas antisepalous stam en pairs orantipetalousonesare a secondary nature ofthe alternate arrangem ent.Futhercarpelprim ordium (orrudim entary carpelprim ordium in the m alefloralbud) w ere form ed centripetally,m oreorlessalter- nating w ith the previous ones atsubsequently higher levels.The generaltypes offloralconstructure in Alism ataceae should be revised.Ascom pared w ith the relative genusofAlism ataceae,thecharacteristics offloralconstructure are discussed in relation to the phylogenetic position ofS.guayanensis.