CO2fixation byCUSCUTA EPITHYMUM. —Seedlings ofCuscuta epithymumor filaments detached from the host(Trifolium repens)fix carbon dioxide by mechanism(s) which are, though to a different extent, stimulated by light. Chromatographic analysis of plant extracts that have assimilated C14O2indicates that, in all cases, the radioactivity is detectable in the areas corresponding to the organic acids and the acidic amino acids. No labelling was associated in appreciable amounts with 3-pho-sphoglycerate and the mono- and diphosphate esters of hexoses and pentoses. Such results are substantiated by the finding that cell-free extracts of seedlings and filaments fix carbon dioxide by carboxylating phosphoenolpyruvic acid. It is concluded that, under the experimental conditions, malic enzyme, pyruvate carboxylase and ribulose-1,5-diphosphate carboxylase have little, if any, significance in the fixation of carbon dioxide by the tested species ofCuscuta.