PAPERS ON BIOLOGY AND AGRICULTURE 173 



An extraordinary deviation from the ordinary course of 

 succession in the county today is exhibited by an area out- 

 side of that of the Rock River woodlands but worthy of note 

 here because of its developmental relation. In the south- 

 west part of Ogle County on the flat top of a Galena lime- 

 stone cliff on Pine Creek there are about twenty acres of 

 dense grow^th of Pinus strobus some seventy to ninety years 

 old. The entire potential area may be said to be approxi- 

 mately a hundred acres or so. 



Early settlers state that about 1840 the white pine 

 growth extended irregularly along Pine Creek for a num- 

 ber of miles and reached out in places on either side of the 

 creek, with a number of groups of dense stands like the 

 one remaining. The species is undoubtedly a relic that ex- 

 ists now in the county only in a few small patches or as 

 occasional individuals in inaccessible localities, those un- 

 fitted for farming and for grazing, and possibly also such as 

 have been in the past fairly secure from damage by prairie 

 fires. 



This Pine Creek stand, whatever its manner of origin, 

 is today and has been for some years past a remarkably 

 strong seedling center. Adjoining it on the east is the cus- 

 tomary oak upland woodland of the county. The pre- 

 vailing winds are from the west and these scatter enor- 

 mous quantities of pine seed from these vigorous trees to 

 the eastward on favorable seeding ground. But here oc- 

 curs the stand of upland oaks. It must be observed, how- 

 ever, that these are two extremely different habitats lying 

 alongside each other. The one, on which the pine is grow- 

 ing, is a shallow, residual limestone soil with rock outcrop. 

 The other, on which the upland oaks are growing, is a 

 deep, upland timber soil of yellow-gray silt loam. The for- 

 mer is of much lower soil moisture content. 



When the pine stand was of somewhat smaller extent it 

 is probable that some oaks grew on what is now pine 

 area. Perhaps certain small portions, or crevices in the 

 latter, furnished greater soil moisture than the limestone 

 pine area in general, thus permitting the oaks to grow there 

 before they had to meet competition from the pines. The 



