170 



IOWA ACADEMY OF SCIENCES. 



The Missouri carries large amounts of finely suspended 

 matter and the tbrovvinCT up of this along the shore lines 

 causes the formation of the higher places in the flood plain. 



The most prominent of the grasses here is Andropogoti 

 provincialis. Panicum virgatiim is also common. Helianthiis 

 maximiliani also occurs on the borders of the meadows. 



Species of the alluvial region of the Missouri and their 

 origin. 



Ranunculus septenirtonalis (E.). 

 Ranunculus abortivus (E.)- 

 Nasturtium terrestre (E. ) . 

 Viola pahnala war . cucullata (E.)- 

 Crotalaria saffittalis (E. ) • 

 Clycyrrhiza lepidota (W. ) . 

 Strophostyles angulosa (E. &• S.). 

 Potentilla Noivegica var. mille- 



gtana ( W.) . 

 CrypototcEnia Canadensis (E.) . 

 Cicuta fnaculata (E. & N.). 

 Vernonia fasciculata (E. & S.). 

 Solidago serotina (E.) 

 Boltonia aete roides ( E . & S . ) . 

 Aster et coides (E . & S . ) . 

 Erigeron Philadelphicus (E.) 

 Iva xatithiifolia (W.) . 

 Ambrosia trifida (E ). 

 Xanthium Canadense (E. & S.)- 

 Helianthus annuus (W.). 

 Helianthus grosse-serratus ( W . ) • 

 Helianthus ntaxifniliani (W.)- 

 Bidens chrysanthetnoides (E. ) 

 Scirpus lacustris (Cos.). 

 Panicum virgatuin (W. & E.). 



Mivtulus ringens (E. & §.)■ 

 Verbena hastatata (E. & S.). 

 Teucrium canadense (E. ) . 

 Acnida tuberculata (S.) . 

 Amarantus alba (W.) . 

 Rumex verticil latus (E. ) . 

 Polygonum ramosissimu'm (Sr. ). 

 Polygonum Virginiatium (E,). 

 Polygonum lapathtfolium var. incar- 



natum (S . ) . 

 Polygonwm Muhlenbergii (E. &: S.). 

 Polygonum PennsylvanicumiY,. &S ). 

 Shepherdia argentea ( W. ) . 

 Euphorbia marginata (W.) . 

 Euphorbia serpens ( W . & S . ) . 

 Euphorbia glyptospenna ( S . & W . ) . 

 Euphorbia Geye'i (W.) 

 Juncus tenuis (Cos. ) . 

 Typha lati folia (Cos.). 

 Spa'ganiutn eurycarpum (E & W.). 

 Alisma Plantago war. Ainericana (E ) 

 Echinodorus lostratus (S. & W.). 

 Cy penis diandrus (E. & W.). 

 Andropogon hcrcatus (E. & W.). 

 Sparti?ta cynosuroides E. & W.). 



OLDER FLOOD PLAINS. 



During glacial times the Missouri carried large volumes 

 of water and much of the present flood plain was a huge 

 stream of water, being augmented by several streams of 

 considerale size like the Boyer, Floyd, and Big Sioux, wath 

 inland lakes some of which like Lake Manawah near Coun- 

 cil Bluffs still exist, these lakes being formed by the 

 washing of sediment at the mouth of the streams, by the 

 deposition of fine silt. The water of the streams flowing 

 through these flood plains is so slow that the backwater 



