| Inner Mongolia West Erdos Steppefied desert region is situated on the rim of ancient Mediterranean sea, many ancient relic species in the desert form the main part of flora of the region. Most of them are constructive or dominant species, their existence play an important role in maintaining the ecological environment in the region. In this study, We select 3 species living in the region, Tetraena mongolica Maxim, Ammopiptantus mongolica and Potaninia mongolica, several key phases in their life history like breeding system, embryological development, seed formation and broadcast mechanism are studied, their reproductive strategies of long-term adaptation to environment and weak links in the life history are researched. Following are the results:1. In the anatomic structure of flower, we find some clear characters of cross-pollination in Tetraena mongolica Maxim and Ammopiptantus mongolica, for example, floral nectary and distyle. Many kinds of insects are observed in Ammopiptantus Mongolica. Experimental results shows that cross-breeding is the main way of reproduction while self-compatibility as supplement in Tetraena mongolica Maxim. Potaninia mongolica is more inclined to self-pollination.2. Following are the features of embryological development: (1)Abortion and abnormality are observed in the formation of microspores and development of male gametes. Most of the abortions are found in two phases—Meiosis phase of microspore mother cells accompanied with early disintegration of tapetum,and matured pollen phase accompanied with various kinds of abnormal development. (2)Different characters are found in the formation of megaspore and development of female gametes: Matured Tetraena mongolica Maxim embryo sac are formed by 4 cells-1 egg cell, 2 synergid and 1 central cell. Matured Ammopiptantus mongolica embryo sac belongs to Polygonum type,while somatic aposporous embryo sacs are formed in Potaninia mongolica (3) As Hieracium type, apomixis is firstly reported in Potaninia mongolica,...
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