中文摘要：

中国灰石藓属长期缺乏系统的形态特征描述和种间区分特征研究，分类鉴定较为困难。该研究采用经典分类学方法，通过查阅灰石藓属内相关物种的原始文献，借阅该属在中国有记载的3个物种的相关模式标本，同时搜集和观察来自美国、加拿大、俄罗斯、瑞典、瑞士、挪威、尼泊尔的标本以及中国内蒙古、四川、新疆等地的地方标本，确认了该属物种在中国的分布，增加了直叶灰石藓在内蒙古和新疆以及灰石藓在四川的新分布记录，并提供了详细的形态描述和图版，编制了中国灰石藓属植物的分种检索表。这3个物种在植物大小、叶是否具褶皱、茎叶和枝叶是否同形等特征上具有区别。该文增补的分布信息及种间区分特征可为中国灰石藓属及棉藓科相关类群的鉴定工作提供依据。

英文摘要：

The long-term lack of systematic morphological characteristic descriptions and species distinctions of Or- thotheciurn Bruch ＆ Schimp in China resulted in the difficult taxonomy. For further understanding of the classifica- tion of this genus, in addition to the study of original literatures of the related Orthotheciurn species, morphological characters of types and general specimens were observed. The specimens examined were collected from the United States, Canada, Russia, Sweden, Switzerland, Norway, Nepal and China（Inner Mongolia, Sichuan and Xinjiang）. This study confirmed this genus species distribution in China. O. intricaturn （Hartm.） Schimp was newly recorded in Inner Mongolia and Xinjing, O. rufescens （Dicks. Ex Brid. ） Schimp newly recorded in Sichuan. Detailed morpho- logical descriptions, illustrations and a key of three Orthotheciurn species were provided, promoting for the taxonomy study of Orthotheciurn and Plagiotheciaceae.