Previous work (by Rostofer, 1970) covered the photosynthetic physiology of two common bryophyte species (Bryum antarcticum and B. Argenteum) found in the melt-streams from glaciers in the Dry Valleys by growing them in a lab using elevated carbon dioxide levels to determine optimal temperature range. This work was repeated using natural carbon dioxide levels and plants that had been collected ... minutes before their use. Micrometeorological parameters were measured for actual environmental conditions around the plant. Infra-red gas analyser were used to analyse the carbon dioxide exchange by each bryophyte. The relationship between photosynthesis and light level was examined, and temperature, light and carbon dioxide concentrations curves were constructed. Infra-red gas analysis of CO2 exchange by soil was measured and Dry Valleys soils were compared with New Zealand soils.