56 



From the foregoing facts, one may conclude that a seam of 

 peat was laid down in a swamp during Aftonian or early Kansan 

 time. As the ice sheet approached, a glacial lake formed in which 



Camera lucida drawings of spores: — (1) Juglans or Carya — 58m; (2) Lyco- 

 podium lucidulum — 32/j.; (3) Juniperus or Larix — 26/x; (4) Betulaceae (perhaps 

 Corylus) — 49/* (somewhat distorted); (5) Picea — 71m- 



varved clays were deposited over the peat. A critical study of 

 the plant remains shows that a northern coniferous plant cover 

 was present in southeastern Minnesota during the Aftonian 

 interglacial or the early Kansan glacial period. 



University of Minnesota 

 Minneapolis, Minn. 



Literature Cited 



(1) Erdtman, G. and Erdtman, H. 



The improvement of pollen-analysis technique. 

 Svensk Botanisk Tidskrift. 1933. Bd 27. H. 3. 



(2) Kay, G. F. and Apfel, Earl T. 



The Pre-Illinoian Pleistocene geology of Iowa. 

 I. G. S. Vol. 34. 1928. pp. 1-305. 



(3) McGee, W. J. 



On the relative positions of the forest bed and associated drift forma- 

 tion in northeastern Iowa. 

 Am. J. Sc. (3) 15. 1878. pp. 339-341. 



(4) Orton, Edward 



On the occurrence of a peat bed beneath deposits of drift in south- 

 western Ohio. 

 Am. J. Sc. Vol. 50. 1870. pp. 54-57. 



(5) Winchell, N. H. 



Geological and natural history survey of Minnesota. "Geology of 

 Mower County." Vol. 1. 1882. pp. 347-366. 



