IOWA AC VDEMY OF SCIENCES. 175 



system. The divide, separating these two systems, passes 

 southeasterly across the center of Union county, thence south- 

 ward near the line of Decatur and Ringgold counties. Adams 

 county rolls southwesterly and is drained by the Nodaway 

 system, which system also drains the eastern portion of Mont- 

 gomery and Page counties, the river system flexing from a 

 southwesterly to a southerly direction, in the southeastern 

 portion of Montgomery county. Taylor county has the Piatt 

 river system, and rolls to the southward. 



The western portion of Montgomery county is drained b}^ the 

 Nishnabotany system, which runs southwesterly, crossing the 

 northeastern portion of Page county; thence bearing westward 

 to Riverton, in Fremont county, where the different systems of 

 the Nishnabotany unite into a single stream; the whole system 

 lies east of the loess hills which border the Missouri river bot- 

 toms. The river systems of the rectangle, in general, flow 

 southwest, except in the extreme eastern portion, where they 

 flow southeast. The whole county is cut into numerous north 

 and south divides by the many tributaries of the Piatt. 



Throughout this rectangle of six counties, the flora presents 

 a complex nature, which is common throughout the region. 

 The native flora is much restricted in extent, though it persists 

 in many portions where the primeval sod has as yet been 

 unfurrowed. The waysides, the narrow strips along the rail- 

 way, and portions next the back settlements, still grow the 

 original prairie grass and the accompanying flora, while many 

 similar tracts are continuously pastured, and present little 

 flora, except here and there a thicket. 



In this region the western flora is passing eastward and the 

 eastern flora westward. Many species, on their tramps in 

 opposite directions, seem to have met in this region, and 

 established themselves, and to have become an integral part of 

 the flora. Examples of the western forms are Lactuca 

 puJchella D. C, Plantago aristata Mx., Solanum7'ostratum Dunal., 

 Hordeum pusUlinn Nutt., and many others as will be seen from 

 the list. Among those moving westward are the Lepidiums, 

 Brassica nigra Koch., Capsella bursa- pastor is Moench., Xanthium 

 canadense Mill., Ambrosia arteiaiscefoUa L., and A. trifida L., 

 AntJwmis cotula D. C, Datura stramonium Li. and D. tatula L , all 

 of which are becoming conspicuous in the waste land through- 

 out the region. The prairie portions yield Silphiums, Heli- 

 anths, Liliums, Psoraleas, Anemones, Ceanothus, Asters, and 



