THE FERN BULLETIN 



VOL. XL 



JULY, 1903. 



NO. 3 



By T. J. and M. F. L. Fitzpatrick. 



THE FERN FLORA OF IOWA. 



V.1BRARY 

 NEW YORK 

 BOTANICAL 

 GARDEN 



Iowa is a great State, wedged between two grand rivers. 

 Her surface rolls like the waves of a peaceful sea. No moun- 

 tains with perpetual snows, no grand gorges, no desolate wastes 

 are to be found within her borders. Here Nature gave birth to a 

 beautiful land where the rewards for tillage are great. 



In prehistoric periods Iowa was invaded five times by the 

 ice from the north, but as milder weather came the ice retreated 

 and left the surface covered with the debris of the wreck and ruin 

 of the invasions. However, a small portion of the surface in 

 northeastern Iowa was not covered by the ice, but stood out as 

 a bold island in the midst of a frozen sea. This portion is called 

 the driftless area, and being more broken and picturesque than 

 other portions of the State, it has received the name of the 

 Switzerland of Iowa. Along the Mississippi river, bluffs of mod- 

 erate height, covered by the primeval or the younger forest and 

 pierced by ravines of greater or less length are of frequent oc- 

 currence. In many places along the river the country rock comes 

 to the surface in the ravines or as cliffs facing the river or its 

 tributaries. 



Beginning in northeastern Iowa, the rocks exposed in suc- 

 cession southward to the State line, are the Saint Croix sand- 

 stone of the Cambrian era ; the Oneota limestone, the Saint Peter 

 limestone, the Trenton limestone, the Galena limestone, the Ma- 

 quoketa shales, the Upper Silurian limestone of the Silurian era : 

 the Independence shales, the Cedar Valley limestone, the Mont- 

 pelier sandstone, and the Lime Creek shales of the Devonian 

 era. and lastly the Carboniferous formations. In northwestern 

 Iowa the Sioux quartzite is exposed. Along the Missouri river 



