POLYMORPHISM IN THE DESMID MICRASTERIAS LATICEPS AND ITS TAXONOMICAL IMPLICATIONS1

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Abstract
SUMMARY: This paper refers to a case of polymorphism in the desmid Micrasterias laticeps Nordst. It is based on material collected from an artificial pond in the state of São Paulo, Brazil.A detailed examination of almost 400 specimens permitted the authors to give a detailed description of 13 main morphological forms of the alga and allowed them to draw the following conclusions: (1) For delimitation of genera and infrageneric taxa in desmids it is often necessary to examine sample populations; (2) the morphological characteristics presently used for delimitation of varieties in M. laticeps Nordst. seem to have no considerable taxonomic significance if isolated individuals are studied; (3) it is necessary to take into consideration Cosmarium arthrodesmiforme Borge and C. arthrodesmiforme var. latius Krieg. & Gerl., as well as M. laticeps Nordst. var. ampliata Krieg., when further studies are undertaken, because they may prove to be merely distinct morphological expressions of M. laticeps Nordst var. laticeps.