封面植物简介--绵刺

绵刺（Potaninia mongolica Maxim．）隶属于蔷薇科绵刺属，只含有绵刺1种。它以花萼3、副萼3、花瓣3、雄蕊3等性状而区别于蔷薇科任何其它属的植物，有“三瓣蔷薇”之美称。其茎多分枝，具宿存、坚硬而成刺状的老叶柄；叶为三出复叶；小叶革质，顶生小叶3全裂，裂片与侧生小叶同形，全缘，两面具长绢毛；叶柄短、坚硬，宿存；托叶膜质，贴生于叶柄。花单生叶腋，花瓣白色或浅粉红色；雄蕊短于花瓣；子房上位，长卵圆形，密生绢毛，花柱基生。瘦果长圆形，淡黄色，为宿存萼筒所包被。绵刺为强旱生小灌木植物，主要生长于具有薄层覆沙的沙砾质荒漠、山前洪积扇和山问谷地，常形成绵刺群落，是沙砾质荒漠的建群种。

Introduction to Front Cover Plant: Potaninia mongolica Maxim.

Potaninia mongolica Maxim, a species of the monotypic genus Potaninia, belongs to the family Rosaceae. It is well known for its tripetalous flowers distinct in the Rose Family, with sepals 3,petals 3 and stamens 3. Stems branched, with persistent ,hard and spiny old petioles;leaves ternate,with terminal leaflets tripartite ,villous on both sides ;stipules membranaceous,adnate to petioles ;flowers axillary, solitary,with white to pink petals ; stamens shorter than petals ; ovary superior, oblong-ovate, densely pilose;fruits oblong,slightly yellow,included by persistent calyx tube. The species is a strong xerophyte,growing mainly on sandy desert area and often forming communities in alluvial fan and valley covered with a thin layer of sand between mountains.