To test the effect of weak alkali on red-pigmented species of Sphagnum, a solution of sodium bicarbonate in water was applied to 17 species in 6 sections of the genus. Species tested in the sections Rigida [S. compactum]. Subsecunda [S. pylaessii, S. cyclophyllum, S. lescurii and S. subsecundum] and Cuspidata [S. recurvum] did not change color (or in sect. Subsecunda became redder). S. magellanicum (sect. Sphagnum) turned dark brown-black. S. wulfianum (sect. Polyclada) turned chocolate brown. The remaining 9 species in sect. Acutifolia [S. russowii, S. warnstorfii, S. bartlettianum, S. quinquefarium, S. rubellum, S. tenerum, S. subnitens, S. angermanicum and S. molle] turned blue or dark blue. The chemical test was equally effective on fresh, freshly dried and herbarium material. At present the significance of this test is unknown since the chemical nature of Sphagnum pigments is only now being determined.