CRETACEOUS FLORA OF WESTERN IOWA. 



I79 



leaves for a thickness of several inches as if the wind had piled 

 them up and the}' had become fossilized in this state. Some 

 of the leaves are preserved in such a perfect state that they 

 must have grown at, or at least very near the place where 

 thev were found; transportation from a distance would cer- 

 tainly have more or less damaged them. 



If we ma}- take the character and perfection of the fossils 

 as evidence we can picture to ourselves the surroundings of 

 Sioux City in the early Cretaceous as a scene of swamps and 

 bavous with an occasional strip of high land which was cov- 

 ered by a mixed forest. The autumn winds that shook the 

 leaves from the trees carried them to the marshes where they 

 became water-soaked, sank, and were buried under the sedi- 

 ments borne in by streams swollen with autumnal rains. The 

 finer silt sifted through the coarser sand and thus softly cov- 

 ered and preserved the leaves in the minutest detail to the 

 present day. 



The following species have been authenticajj.^^ determined: 



I. POPULUS KANSASEANA Z^5^. ^^-''"^ 



Lesq., Fl. Dak. Gr., U. S. G^jT^urT^Mon. XVII.., X.42, 



PI. XVII., Figs. 1-7. \ r.':';'''^ •■^^'^i^ X 



Three specimens in a fair state or^pKes^i:vatipij are^Mfuie 

 collection. 



2. POPULUS HYPERBOREA Hce7\ 



Heer, Fl. Foss. Arct., vol. 3, pt. 2, p. 106, PL XXIX., Figs. 

 6-9; PI. XXVII., Fig. 8d; PI. XXX., Fig. 2b; vol 6, Abth. 2, 

 p. 64, PL XXVII., Figs. 6, 7; PL XXL, Fig. i a. Lesq., FL 

 Dak. Or., U. S. Geo. Sun, Mon. XVII., p. 43, PL III., Figs. 

 9-1 1 ; PL VIII., Fig. i; PL XLVIL, Fig. 5. 



A single good specimen is listed. 



3. Salix protEv^kolia var. Longifoi.ia Lesq. 



Lesq., Fl. Dak. Gr., U. S. Geo. Sun, Mon. XVII., p. 50, 

 PL LXIV., Fig. 9. 



Several fragments occur most of which show characteristic 

 details well. 



Ill— 4. G 



