172 IOWA ACADEMY OF SCIENCES 



Ambrosia trifida. The Ambrosia trifida being the 

 immediate foreunner of small shrubs and trees. 



The drainage along the stream is naturally more perfect 

 than the soil away from the flood plain, the soil is better 

 areated, hence trees can grow here. One of the first woody 

 plants to appear is Sallx nif/ra which overhangs the 

 streams, Salix ami/r/daloides is also an early tree replaced 

 later by Negundo aceroides, Ulmns americanas, Populus 

 mo)iiIifera and Fraxiuus riridis. Of the woody climbers the 

 following may be mentioned. 



Viiis riparia. Ampelopsis quinquefolia . 



Menispermum canadense . Rhus toxicodendron. 



of the herbaceous climbers the following appear in these 

 young forests 



Echinocystis lobata. Huntiihis hipulus. 



and shade loving plants like 



Itnpatiens pallida. Coreopsis connatus. 



Bidens frondosa. Urtica gracilis . 



UPLAND. 



THE RAVINE. 



Owing to the peculiar loess formation in the Missouri 

 valley region very few ravines in their younger stages cai] 

 be seen, at least not in the west slope of the hills. It is 

 only through the removal of loess material for manufac- 

 turing or grading that these embryonic ravines occur. 

 Where such are found very little vegetation occurs. The 

 vertical faces of the bluffs are in many cases one hundred 

 feet high. On the bare faces one sometimes finds Rosa 

 blanda vdiX. Arkansana and Li/fjodesmla jtincea deeply rooted 

 in the soil. Very few land slides occur except where there 

 is a considerable growth of herbaceous plants and the 

 formation is underlaid by a sheet of water. At the base 

 of these hills plants like Gaura coccinea, Sporobolns citspi- 

 datiis, Laduca piilchella occur. The characteristic plants 

 of the ravine beginning at the base are as follows: 



