SPORE MORPHOLOGY IN THE GENUS BRUCHIA SCHWAEGR. (MUSCI)

Scanning electron microscopy observations of the spores of Bruchia have resulted in the recognition of four spore types based on the ornamentation of the distal spore surface: warty or verrucate, pitted, reticulate, and spinose. The proximal surface of the spores of all species, except B. brevipes, is characterized by a central aperture region surrounded by a triangular murus or rows of spinae forming a triangle and 1 or 2 smooth or verrucate collars. The ornamentation patterns observed are considered to be characteristic for the genus. Spore morphology alone can rarely be used to distinguish species but in conjunction with certain other characteristics, it is an important taxonomic feature. Spore morphology is a major characteristic used to define the limits of the highly variable species B. flexuosa (spinose spores) and to distinguish it from the closely related species B. texana (reticulate spores). Variations in ornamentation patterns within the genus support the recognition of two subgenera (subgenus Bruchia and subgenus Sporledera). Spore morphology also supports the close relationship between Bruchia and Trematodon and is sufficient to eliminate several questionable taxa from the genus.