中文摘要：

为探讨缺齿藓类与真藓科、提灯藓科的系统关系,理清缺齿藓科的系统位置和中国缺齿藓科分类问题,该研究以中国分布的缺齿藓科植物和相关类群4 000余份标本为材料,进行详细的形态学研究,并选用其中35种、40份样品的4个DNA片段（rps4、trnG、trnL-trnF、atpB-rbcL）联合数据用于分子系统分析,采用邻接法（NJ）和最大似然法（ML）构建分子树。结果表明：（1）在分子树中,缺齿藓类与真藓科植物分别聚在具有高支持率的不同分支上,叶形、叶细胞等形态学特征也有较大差异,缺齿藓类应从广义的真藓科分出。（2）在分子树中,虽然缺齿藓类与提灯藓科植物聚在同一分支中,但无形态学的共源性状,二者不应视为一个单系类群。（3）缺齿藓科是一个自然类群,缺齿藓科内属间存在着密切的系统关系,缺齿藓科的主要识别特征为：植物体小型,茎常分枝;叶形和叶细胞为丝瓜藓型（Pohlia-like）,披针形至长椭圆形,中上部细胞狭长,线状菱形或蠕虫形;生殖苞多生于新生枝顶;蒴齿为互生双齿层,常有不同程度的退化或一层蒴齿缺失,稀双层蒴齿缺失。（4）中国缺齿藓科包含有5属,即缺齿藓属（Mielichhoferia）、丝瓜藓属（Pohlia）、拟丝瓜藓属（Pseudopohlia）、合齿藓属（Synthetodontium）和小叶藓属（Epipterygium）,目前为止共计34种（含种下分类单位）。

英文摘要：

The paper aims to discuss the relationship between Mielichhoferiagroup and Bryaceae ,to identi-fy morphological synapomorphy between Mielichhoferiagroup and Mniaceae ,to solve the problem of sys-tematic position of Mielichhoferia group ,to figure out the classification of Mielichhoferiaceae in China . Morphological characters of more than 4 000 specimens of Mielichhoferiaceae and its related groups in Chi-na were analyzed .And then ,neighbor joining （NJ） and maximum likelihood （ML） tree were built based on combined trnG , rps4 , trnL-trnF ,and atpB-rbcL cpDNA sequences of 40 specimens for 35 species . Combining morphological and molecular data in the analyses showed that ：（1） not only were Mielichho f e-ria group and Bryaceae family in the different clades in the molecular tree ,but also morphological features , such as the leaf shape ,the leaf cells of the two groups were different .Mielichho f eria group should be sep-arated from Bryaceae .（2） No morphological synapomorphy can be detected for Mielichho f eria group and Mniaceae family ,although they were in the same clade in the molecular tree .The two groups were not monophyletic .（3） Mielichhoferiaceae is a natural monophyletic group .In Mielichhoferiaceae ,the plants are small ,stems tend to be much branched than in Bryaceae ;leaves are Pohlia-like in shape and areola-tion;gametangia are often produced on lateral branches or the base of stems ;peristome is diplolepideous-alternate ,often reduced to one layer or rarely absent .（4） There are five genera ,Mielichhoferia ,Pohlia , Pseudopohlia ,Synthetodontium and Epipterygium ,in Mielichhoferiaceae in China ,total 32 species and 2 variaties .