Contribuição ao estudo dos corpos silicosos das gramíneas amazônicas I. Panicoideae (Melinidae, Andropogoneae e Tripsaceae).

Abstract

The present paper is an initial contribution to the publication of a catalog of the silica bodies of the Amazonian grasses. It is hoped that studies comparing phytoliths with silica bodies will elucidate the origin of the "cerrados" of the Amazonian region as well as be an aid to the taxonomy of the family. We have studied the genera of the tribes Melinideae, Andropogoneae and Tripsaceae of the subfamily Panicoideae. The material used was taken from the Herbaria MG, IAN and INPA, where there are good collections of Amazonian grasses named by specialists. The technique used consited of burning the leaves in a clay crucible in a eletric oven at a temperature of 800ºC for about 15 minutes, mounting the ash in Canadá balsam, and drowing the silica bodies with aid of a camera lucida. The results show that in a few cases there are intergeneric and interspecific distinctions in the morphology of the silica bodies. The conclusions of this first study emphasize the need for a more detailed investigation of a larger number of genera and species in order that silica bodies may be used to full effectiveness in the systematics of the family.