observed in the list. The greater part of this flora, however, as 

 in all the sandy areas, consists of prairie plants, and where the 

 dunes and upland sands become well established, the prairie 

 flora t&kes complete possession, as is illustrated in most of the 

 area represented in Plate V, fig. 3. 



Sometimes the plant covering also passes into forest. The 

 transition from bare dune, as shown in Plate II, fig. 1, through 

 the series illustrated in figs. 2 and 3 of the same plate, to Plate 

 III. fig. 1, may be obser^'ed in many places in the Harrison county 

 area. The transition usually occurs from Salix longifoUa and 

 Amorpha fruficosa, of low grounds (see Plate I, fig. 3), and 

 Salix missouriensis, Cornus paniculata, and Zanihoxylum amer- 

 icanum of the dunes, to Popidus deltoides, Salix amygdaloides, 

 Acer negundo, Crataegus mollis and JJlmus amencana, Popidus 

 being the dominant species. 



In the Muscatine dune region, a similar transition to oak forest 

 may be obser^^ed. Plate V, fig. 1, illustrates this. The light 

 spot on the fixed dune in the background shows a ''blow-hole^' 

 with shifting sand. The only plants on portions of this are mats 

 of Mollugo verticillafa (see fig. 2 on the same plate) ; then fol- 

 lows a scattering of Croton- capiiaius, Cenclirus. and Polanisia-, 

 the vegetation then becomes denser and consists in part of sand- 

 species such as Oenothera rhomhipetala, Cyperus Schweinitzii, 

 and Carex ceplialopliora, but chiefly of prairie species, such as 

 Panicum Scrihnerianum, AmorpJia canescens, Rosa pratincola, 

 and other typical prairie forms: then clumps of Rhus canadensis 

 var., Vitis vuJpina, etc., form a transition to the forest in the 

 background, which consists of Que reus velutina at the margin, 

 with other hard-wood upland species in the deeper forest. 



The flora of the sandy ridges, listed in column VI does not 

 differ in important particulars from that of the dune regions, 

 excepting that there is a smaller number of t}T)ical sand-plants, 

 and a more complete blending with surrounding prairie and 

 forest floras. 



The sand-talus flora is limited, and contains no species which 

 does not occur in the other areas. The sand is quite sterile and 

 the plants are mostly decidedly dwarfed. 



The preponderance of prairie plants on these sandy and grav- 

 elly areas is of special interest because it demonstrates the fallacy 



11 



