IOWA ACADEMY OF SCIENCES. 63 



i. 



rom the numerous spriiii^s. The more conspicuous trees 

 found here are Picea pnnf/ens, Popiilus anf/iistifolia, P. trem- 

 iiloiiJes, Betula occidentalis, and Almas Incana var virescens. 

 A good undergrowth of Thermopsis niontiuia, Salix sps. 

 (reraniuni Richardsonii, Vicia Americana, Gemii macrophyl- 

 linn, Alluim hrevistylmn, Ayropf/ron Richardsonii and A. 

 pseado-repens is found here. 



The mesophytic area is decidedly irregular. The second 

 flood plain presents a series of irregular open parks, con- 

 taining scattered groves of Picea punyens, a few groves of 

 Popidns angiistifolia in the more moist situations, scat- 

 tered trees of Janiperns occidentalis var monosperma, but 

 the most conspicuous plant is Artemisia tridentata. 



This belt is essentially xerophytic, and has been evolved 

 from the mesophytic. The surface soil is a sandy loam; 

 l\ing underneath are bowldeis of various sizes. Very little 

 humus remains, owing to the repeated washings of spring 

 freshets. 



The more common herbaceous plants found here are as 

 follows: Cnicus Drummondii var acaulescens, Aiitennaria 

 sp., Campanula rotund ifolia, Agropyron occidentale, Erig- 

 g()}ium umhellatum, Elymus coudensatus, Stipa viridula, 

 Lupinus argoplujlius, Penstemon sp. The Populus augusti- 

 folia, Potentilla fruticosa, Juniperus communis, Arctosta- 

 pliylos, Ura-ursi, are remnants of an aiea once densely 

 wooded like the present flood plain. Along the shorelines 

 of this flood plain are springs, receiving their water from 

 the third flood plain and table lands. The water in these 

 springs is uniform during the season and registers 49° ¥.: 

 these springs contain many hydrophytic species Jike Spiro- 

 gyra, Veronica Americana, Ranunculus Cymhalaria, Mimu- 

 lus Jamesii on the edge, Catfabrosa aquatica and Carex. 

 These springs are always bordered by willows. More com- 

 plete drying of the bench lands above, by a smaller amount of 

 snowfall during the winter would destroy the present meso- 

 phytic vegetation bordering on these springs and turn it 

 into a xerophytic park with its Juniperus and Artemisia. 



The third flood plain forms a wide valley, treeless, except 

 where intersected by streams. This area is marked by 



