Bryum capillare Hedw. is a cosmopolitan moss ubiquitous in cities, where it occurs as a dense-green velvet growths between the cracks in sidewalks. We report on the cyanobacterial and algal associates of B. capillare and the role they have in building biogenic crusts. Individual plantlets of B. capillare are cultured on 1/5 strength Hoagland’s 1% agar medium. After five days a variety of cyanobacteria and algae are observed growing out from B. capillare implants. Some of the more abundant cyanobacterial taxa observed are: Lyngbya sp., Calothrix sp., Osillatoria sp. Phormidium sp., Hyrocoleum homeotrichum, Anabaena sp. Anabeana circinalis, Synechocysitis aquatilis, Shizothrix sp. Among the eukaryotic algae present are: Klebsomium sp. Ulothrix sp. and an unidentified diatom. Most of these cyanobacteria and algae are filamentous. This morphology probably adds a textile-like resiliency to the biogenic crust. Based on these observations it is hypothesized that the laying down of a cyanobacterial/algal mat is a prerequisite for B. capillare colony growth. This suggestion is supported by the field observation of a biogenic crust of cyanobacteria and algae subtending B. capillare colonies. This study is ongoing and should have applications to moss ecology and processes of primary succession.

Key words: algae, biodiversity, biogenic crusts, Bryum capillare, cyanobacteria, primary succession