This volume is the last contribution of a series of With the present book, a further gap concern- studies concerned with the plant material of one ing leaf morphology and leaf venation, as well and the same area of Venezuelan Guiana. The as some structural peculiarities of physiological importance, is closed so that an exhaustive survey studies originated through a collaboration with the forest engineer Dr. B. Rollet, the FAO expert in of bark and leaf morphology and anatomy as well forest inventory who collected the material of tree as of fruit and seed structure of the plants of a barks, leaves, fruits and seeds in Venezuelan certain well-known area is herewith given. Not Guiana around the "e;Rio Grande"e;, "e;EI Paraiso"e;, only were hundreds of species studied, but and "e;EI Dorado"e; camps. In the first place, tree structural characteristics were related to "e;forest barks of about 280 species of dicotyledons stratification"e;, i. e. to the different micro climatic belonging to 48 families were studied (family by conditions in the forest, as the height of the trees family) by Roth in separate publications which and shrubs studied was known. It is of common mainly appeared in Acta Botanica Venezuelica knowledge that in the lower forest layers, light is a and in Acta Biol6gica Venezuelica (see the bibli- limiting factor, while humidity is sufficiently avail- ography in Roth 1981).