On the Flora of the Guayana Highland

Abstract

Guayana Highland is a great upland characterized by the spectacularly eroded Roraima sandstones, associated sediments, and intrusive elements which overlay the ancient immutable basic crystalline Guayana Shield, which with the larger Brazilian Shield to the south gives form and permanence to the continent of South America. Roraima sediments are usually considered to be Cretaceous in origin. It is suggested, on botanical evidence, that the emergence of these sediments may antedate the Cretaceous, and that the original flora, which developed thereupon and persists into this age, was a part of the early evolution and development of the contemporary angiosperm flora. Persisting autochthonous elements are prominent. A preliminary review indicates that the historical relationships of the provincial flora of Guayana lie, in order, with those of: 1) the Brazilian Highland; 2) tropical Africa; 3) the Andes; 4) the Caribbean, and 5) Malaysia. magnitude of these relationships requires the early existence of historical land continua. floras of the surrounding Amazon and Orinoco Basins, the Hylea, are youthful. THE FOLLOWING PIECE has been extracted from a paper titled, Isolated Mountain Floras of Guayana (southern Venezuela and contiguous Guyana, Brazil and Colombia) , which was prepared for the symposium, Adaptive Aspects of Insular Evolution, held in Mayagiiez, Puerto Rico. Besides the elimination of sections dealing with comparison of the flora of Guayana with that of the West Indies and contrast with ecologic and distribution modes of the fauna of Guayana, I have deleted considerable other materials from the subject matter there presented. Still, after more than 20 years of intensive activity involving much field work, herbarium study, and collaboration by many competent taxonomists, some 10,000 Guayana plant collections remain to be identified and interpreted. data and conclusions presented at Mayagiiez and contained in this paper are, therefore, to be considered preliminary and incomplete. concluding reports on collected materials and final summation of phyletic implications and the ecology and geography of the Guayanan flora should comprise the three remaining projected parts of The Botany of the Guayana Highland, which would conclude the series being published in the Memoirs of New York Botancical Gar denz. area of the great sandstone and related sedimentary deposits and intrusive volcanics the Roraima Formation-superposed over the crystalline Guayana Shield of northeastern South America is the seat of a distinctive flora of provincial character which must be considered in primary part autochthonous. This phytogeographic province of Guayana may well be contemporaneous in origin and development with that of the Brazilian Shield, certainly older than that of the Amazon Basin (and Orinoco Basin), and probably older than that of the Andean cor-