The effect of culture filtrate (conditioned medium, CM) containing cell exudates obtained from green alga, Scenedesmus subspicatus, on cell suspension of dicotyledonous plant Silene vulgaris was examined. The addition of diluted CM to the modified MS medium, supplemented with dicamba and BAP, stimulates cell biomass production. The biomass was composed of association of single non-dividing cells, cells during mitosis stage and cellular aggregates. Silene cells began mitotic divisions earlier in the presence of CM in medium when compared to control treatments. Results of performed bioassay showed that some factor or factors released by green alga to the culture medium could be responsible for sustained proliferation of phylogenetically distant species cells. Although it is still unclear which culture constituent influenced most the mitotic response of Silene suspension, results point at versatile stimulatory character of green alga exudates in higher plant cell culture.