Part XI of The Botany of the Guayana Highland includes taxonomic and in some cases morphologic, ecologic, and palynologic treatments of 49 genera representing seven families of flowering plants: Tepuianthaceae (a new family of Sapindales) by B. Maguire and J. A. Steyermark; Malpighiaceae by W. R. Anderson; Pakaraimaea (Dipterocarpaceae) by B. Maguire and J. A. Steyermark; Convolvulaceae by D. A. Austin and George W. Staples III; Ebenaceae and Lissocarpaceae by Frank White; and Gentianaceae by Bassett Maguire. Includes keys, descriptions, and black and white illustrations.