Abstract: This is the outcome of a pioneer comprehensive investigation of green-algae of Oxic Dystrustepts soils in the Western Ghats of South India, one of the biodiversity hot-spots of the world exposing very many new species. Seventeen percent of the total species observed are quite new to science. Taxonomical characterization of algae in relation to soil and vegetation is carried out systematically from field soils, 'growth slides' and artificial culture of soil samples in specific media. Physico-chemical soil parameters examined were soil-moisture, pH, total carbon, conductivity, total/Kjeldahl nitrogen, plant available potassium and phosphorus. These are correlated to species richness, species diversity index and relative abundance of all green-algae observed. Desmids are found to be the most dominant group of green-algae in these soils. Since green-algae in general are significant biotic component of all ecosystems search of them in these soils is also worthy. Identification and understanding the ecology of them becomes highly relevant from an economic and conservation point of view of algae as well as sustainable management of the fertility of natural soils. Major goal of this investigation was to assess the biodiversity of green-algae in relation to certain physico-chemical characteristics of soils and three different kinds of vegetation such as natural forests, teak and rubber plantations. Results emphasize the worth of immediate exploratory studies throughout the wet tropical soils especially that in the Western Ghats to account the precious biodiversity of green-algae before they get further affected by soil degradations from diverse factors including global climate change.