Contribuição à Ficologia da Amazônia. 3 - Desmidioflórula dos lagos Cristalino e São Sebastião, Estado do Amazonas: Gêneros Netrium, Closterium e Pleurotaenium ¹

This paper is a contribution to the qualitative survey of the desmids — Mesotaeniaceae and Desmidiaceae, Zygnemaphyceae — from two lakes, Lago Cristalino and Lago São Sebastião in the northern State of Amazonas. Brazil. Samples were galhered monthly during one year. The genera Netrium, Closterium and Pleurotaenium were identified to totaling 11 infrageneric taxa, all of which were described in every morphological detail possible. They were also given measurements and the illustrations needed for the taxonomic identification. Comments about every named taxon are included. An artificial key based on fundamental morphological and vegetative characteristics was prepared for the identifications of the taxa documented in the text. A larger number of desmid taxa were observed to occur in Lago Cristalino than in Lago São Sebastião. The taxon commonly occuring in both lakes was Clasterium lirteatum var. lineatum f. lineatum.