Plate XTX. 



Fig-. 1. Associations on tbe river dune, Hanover area. In the rifjht foreground, the deposit 

 association, with a large bunch of Panicum virgatum and abundant Aristida tuberculosa; behind it, 

 tlie .S' ;«//«(■/«/ association ; in the background the dune thicl^ets, with a dense tang-le of lianes. 



Fig. 2. Margin of the dune thickets on the windward side of the river dune, Havana area. 

 The effect of the raigrati )n of the dune is shown in the exposed roots. Forests of the Mississippi 

 river flood-plain in the background. 



