122 PUBLIC PARKS OF IOWA 



THE FLORA OF THE LEDGES. 

 By Wm. W. Diehl. 



In the south-central part of Boone county is an area that possesses 

 characteristic plants as well as peculiar geological and topographic, 

 features. This is located four miles directly south of Boone and extends 

 for about two miles south toward and along the Des Moines river. Its 

 name, The Ledges, is appropriate because of striking sandstone cliffs from 

 ten to over forty feet in height, extending beyond the perpendicular in 

 some cases as much as twelve feet. This ledge rock here 'comprises an 

 island of younger massive sandstone surrounded uncomformably by some- 

 what older carboniferous layers, which are of different structure. The 

 conditions peculiar to this restricted locality give the flora a distinctive 

 character. 



It is evident from the appended catalogue that this area possesses a 

 flora typical of a forested region or of a region until recently covered 

 with woodland. Originally all or nearly all of this area was wooded. It 

 would seem that the northern limit of the unshaded part of the map rep- 

 resents approximately the northern extension of the former encroaching 

 forest belt. Along the roadside just north of this line are some remnants 

 of such prairie grasses as Spartina Michauxii Hitch, which have not been 

 found within the area in question. That the forest once extended to this 

 line is shown by the presence of tree stumps over much of the area. The 

 stump of a bur oak growing near a clump in this vicinity showed sixty- 

 one annual rings. Residents of the district also attest that practically all 

 this land was once wooded. Of course the wooded area is now confined 

 to the rough land near the river and along the steep slopes of the ravines 

 adjacent. 



The catalogue indicates the somewhat anomalous character of the 

 vegetation of the region. For instance, MOTHS rubra L. and Viburnum 

 Lentago L., which are plentiful just outside the tract to the westward, 

 have not yet been found within The Ledges. Aesculus glabra var. arguta 

 (Buckley) Robinson, while plentiful at Frazer near Boone, and along 

 Honey creek about three miles to the northwest where conditions are 

 somewhat similar, has not been found at The Ledges. ' Anemonella thalic- 

 troides L. is abundant on the bluffs along the Skunk river in Story county, 

 but it has not been collected at The Ledges. Caltha palustris L. covers 

 the marshy southern bank of the Des Moines river to the west of The 

 Ledges, but the writer has been unable to find it within the area in 

 question. 



The Ledges may be said to be characterized by the presence of CJadonia 

 sylvatica, Polytrichum commune, Camptosorus rhizophyllus, Polypodium 

 vulgare, Woodsia obtusa, Trillium nivale, Mitella diphylla, Juniperus vir- 

 giniana, Dirca palustris, Lathyrus ochroleucus, Physocarpus opulifolius, 

 Prunus pennsylvanica, and Rhamnus lanceolata. Iowa Academy of 

 Science, Vol. XXII, excerpt from the proceedings. 



