The Rhacomitrium heterostichum complex in British Columbia consists of four species and five varieties: R. "laxum", R. heterostichum, R. heterostichum var. affine, R. sudeticum, R. sudeticum var. macounii, R. brevipes, R. brevipes var. "laevis", var. "eramulosum" and var. "microcarpiformis". Within each of these taxa minor variations occur. R. sudeticum tends to be confined to sub-alpine and alpine localities and R. heterostichum to lower elevations, while R. "laxum" and R. brevipes show no altitudinal limitations. There appears to be a positive correlation between nature of branching and details of leaf apex structure to moisture conditions: short branches, abbreviated hair point and shorter leaf cells in the leaf apex being commoner in specimens of wet sites than in specimens of dry sites. Experimental evidence is needed to determine phenotypic plasticity in these characters, since they are widely used to distinguish among the various taxa of the R. heterostichum complex. / Science, Faculty of / Botany, Department of / Graduate