Abstract
Rhachithecium perpusillum (Thwaites & Mitt.) Broth. is added to the moss flora of Kyoto Prefecture, Japan. Its closest relative, R. nipponicum (Toyama) Wijk & Margad., was known to lack peristome teeth and found in more detailed observations to have no traces of their formation. Then, the two species can be distinguished on the basis of the immature sporophyte. Rhachitechium perpusillum was previously known to occur in only two locations in Japan. Despite this rarity, colonies speculated to be of this species were found in four urban green spaces in Kyoto City. Interestingly, the sporophytes were only found in one of the locations, and in that colony no sporophytes were seen until three years later. These observations indicate the difficulty of discovering and identifying this species and the possibility of this species being more widely distributed within Japan.
https://ror.org/02kpeqv85 
