Pseudatrichum was described in 1941 from material collected in China by P. C. Chen, and sent to H. Reimers at Berlin; the type collection presumably was destroyed during the War. Reimers' description, though based on sterile and male plants, is quite sufficient to identify the plant, and in recent years, several Chinese workers have described and illustrated this interesting species, and distributed specimens of it.
In my conspectus of the genera of Polytrichaceae (Smith, 1971), I suggested that Pseudatrichum might be a synonym of Oligotrichum armatum Broth., a little-known species from Yunnan. It now appears that Pseudatrichum is widely distributed in Asia, from the Himalayas to the Philippines, and is synonymous with Pogonatum nudiusculum Mitt. The most remarkable feature of this species is the Atrichum-like, diagonally-trending rows of teeth on the back of the leaf. As Reimers himself observed, these are not always so well-developed; in the holotype of P. nudiusculum (NY!), for example, they are relatively inconspicuous. The areolation ofthe lamina is also unusual, with small, quadrate cells, which are strongly mammillose, like those of Atrichum angustatum (Brid.) B.S.G.