19211 TALMER, BOTANICAL RECONNAISSANCE OF SOUTHERN ILLINOIS Ul) 



to one hundred and fifty feet high and measuring from four to six feet 

 in diameter above the swelled base were by no means rare. The bases 

 of such trees were buttressed in a most grotesque and astonishing manner, 

 being frequently fifteen or twenty feet in diameter and surrounded for 

 many yards by the curious aerial root cones or "knees." On account 

 of its value for lumber most of the large trees have been cut down, and 

 those that remain have for the most part escaped only because their 

 trunks are hollow, decayed or in some way defective. Specimens of 

 moderate size are still frequent, however, and remain the most striking 

 feature of the swamp-land forest. 



Other notable trees of the frequently inundated lowlands and swamps 

 are the Tupelo, Swamp Hickory, Water Elm, Sweet Gum, Swamp Honey 

 Locust, Pumpkin Ash, Green Haw {Crataegus viridis), Ironwood {Car- 

 pinus caroUniana), Southern Hackberry {Celtis laevigata), Swamp Maple 

 {Acer ruhrum). Downy Cottonwood {Populus hctcrophylla) , and the Over- 

 cup, Bur {Quercus -macrocarpa) , Basket, Willow (Q. Phcllos), Pin {Q. 

 pahistris), and Swamp \Miite {Q. bicolor) Oaks. Typical shrubs are the 

 Silky Willow {Salix sericea). Swamp Dogwood {Cornus stricta). Button 

 Bush {C ephalanthu s) , Storax {Sty rax americana), Itca, Swamp Rose {Rosa 

 palustris), Swamp Privet {Foresticra acuminata), and Deciduous Holly (//ex 

 decidua). A number of these species, however, extend beyond the limits 

 of the swamps and are associated with many others in the rich and varied 



forests of the wide valleys. 



Since the alluvial flood plains of the great rivers and the peculiar eco- 

 logical conditions that support this flora are best developed in the region 

 about the town of Cairo, as a plant province of southern Illinois, it nuiy 

 appropriately be called the Cairo Formation. Its relation to the general 

 region occupying the lowlands of the ancient Mississippi Embayment 

 and delta and its limits in Illinois have already been indicated. 



Besides the quite characteristic species mentioned above many others 

 common to the surrounding regions grow in the bottom lands and some 

 of them even invade the swamps. Amongst trees and shrubs of this class 

 may be mentioned the Big Scaly-bark Hickory {Carya laciniosa). River 

 Birch {Betula nigra), Spanish Oak, Bur Oak, Red Mulberry, Pawpaw 

 {Asimina triloba). Summer Haw {Crataegus mollis). Honey Locust, Silver 

 Maple {Acer saccharinum). Box Elder {Acer Negundo), Black Gum {Xyssa), 

 Green Ash {Fraxinus pennsylvanica var. lanceolata), False Indigo {Amorpha 

 fruticosa), Button Bush, Southern Black Haw {Viburnum rufidulum). 

 Rough-leafed Dogwood {Cornus asperifolia) , and the climbers Bignonia 

 radicans, Vitis rupestris, V. cordifolia, Parthenocissus quinquefolia hirsuta, 

 and three or four species of Smilax. The woody vines Vitis palmata, 

 Brunnichia cirrhosa and Trachelospermum dijforme are restricted to the 

 swamps or their immediate borders; and from the long list of herbaceous 

 plants the following may be taken as characteristic of the Cairo Forma- 

 tion: Peltandra virginica, Iris fuba. Ranunculus delphinij alius, Radicula 

 aquatica, Hottonia inflata, Hibiscus incanus, Triadcnum virginicum, T. 



