60 IOWA ACADEMY OF SCIENCES. 



GREEN RIVER BASIN, 



The temperature during the day is uniformly high; the 

 heat is greater than the aerial thermometer indicates, 

 owing to great amount of radiation from the earth. So 

 that any plants occurring here must conserve moisture. 

 The soil is parched and dry during the summer and late 

 spring, because of its alkalinity. 



The vegetation of the broad flood plains of Green river, 

 in the vicinity of Green river, is essentially xerophytic. 

 A few scattered groves oi Popiilus an(/usti folia occur in the 

 more favored situations. 



The shrubs and herbaceous plants are more or less scat- 

 tered. The soil is characterized by its tenacity when wet 

 and baked, wdien dry with a wdiite, alkaline efflorescence 

 on the surface. The most abundant grass of the flood 

 plain is Distichlis spicata. The widely distributed Hordeuni 

 juhatum and the western H. caespitosum are common and 

 gregarious species of the lowlands. The Distichlis, owing 

 to its habit of growth, spreads over the surface, to the 

 exclusion of all other vegetation. 



Two capparidaceous plants are common in the open 

 places, Cleome iiitegri folia and C. lutea. both species, owing 

 to their somewhat fleshy leaves are well adapted to this 

 region. These species flow^er during the entire season. 

 The Stanleya pinnati^da is associated with i home. Atri- 

 plex lomjifolia occurs in scattered bunches over the entire 

 flood plain. A further special feature is the occurrence of 

 other chenopodiaceous plants like Sarcohatus verrniculatas, 

 Chenopodium Frewontii, C. rvbrutn, Eiirotia lauata and Siia- 

 eda depressa. 



During the spring of the year the lateral channels con- 

 tain water, but in July and August tliese channels are dry. 

 Here an abundance of Hordeum caespifosum occurs with a 

 scattered growth oillelenium aufumnale and Poteiitilla Anse- 

 rina. The Helenium is usually not more than a foot high. 



Along the imn-ediate shore lines of the river in the cot- 

 tonw^ood groves, Glycyrrhiza lepidota, Symphoricarpos race- 

 mosiis, Rosa Fendleri, Aster and Eriyeron usually grow in 



