absence of Juglans or Carya in the lowan deposit may be significant, 

 but the presence of Tilia, Quercus, and Compositae species in the 

 later deposit may be taken to represent an ecology similar to that 

 suggested by Juglans or Carya. The assemblages of fossils suggest 

 a forest of the transitional type which exists between the northern 

 coniferous forest and the more southern broad-leaf forest of today. 

 The fossil assemblages in both peat beds suggest a forest type 

 that no longer exists within the immediate vicinities of the deposits. 



The graphs (Fig. 1) show that the early forest which developed 

 on the Nebraskan drift, and indicated by the fossils in the six 

 inch level of the peat bed, was that of Picea, Pinus, and Abies 

 type. In addition, a small percentage of Betula and Quercus ex- 

 isted. Two inches above the lower contact (4 inch level), Picea 

 glauca pollen is less abundant and Picea mariana was not found. 

 Abies and Pinus Strobus or P. resinosa are more abundant than 

 in the lowest level, and Quercus has increased in importance. In 

 the two inch level, Picea glauca continues to decrease while P. marl- 

 ana returns to a place of importance in the pollen diagram. Betula 

 increases but Quercus is less important and Acer and Tilia appear 

 for the first time. Abies is absent from this level. With the excep- 

 tion of one additional species (Pinus Banksiana) , the percentages 

 of pollens at the contact of the peat and the Kansan drift is almost 

 identical with those at the contact of the peat and the Nebraskan 

 drift. The return of the tree-pollen percentages at the top of the 

 deposit, to ones similar to those at the lower contact, is sugges- 

 tive of a return of forest conditions like those in early Aftonian 

 time. Such appears to have been the status of the forest near 

 Belle Plaine, Iowa, when it was overridden by the Kansan Ice. 

 The pollen percentages at the upper contact also suggest that as 

 the ice advanced into central Iowa, there was a change from a 

 broad-leaved and coniferous forest, as suggested in the two inch 

 level, to a more general coniferous forest, indicated by the micro- 

 fossils at the upper contact. 



A detail in the development of the peat is indicated by the 

 presence of Sphagnum spores. In Table 1 these are shown to range 

 in abundance from zero percent in the lowest level, to 5.3 percent in 

 the four inch level, and 59.5 percent in the two inch level, and finally 

 back to zero in the uppermost level. These percentages suggest a de- 

 velopment of a small pond into a bog. No macroscopic remains of 



