Southeastern Washington and Adjacent Idaho. 67 



such areas. The broken rock fragments not only aid in the 

 percolation of water and prevent run-off, but also tend to reduce 

 evaporation. 



The xerophytic character of Poa sandbergii has been discussed. 

 Polygonum majus with its wiry stems and diminutive leaves 

 answers well ecologically for a grass. Likewise, the linear-leaved, 

 spiked, densely hairy Plantago may be so considered. 



Polygonum majus must be a plant of very low water require- 

 ment for, in spite of its shallow roots, it blossoms and appears 

 to thrive throughout the summer and fall in these stony soils. It 

 is especially noticeable among the rocks when most other plants 

 are dried out, and its abundance makes it showy notwithstanding 

 its tiny flowers. I have counted more than 1,000 individual plants 

 from 2-8 inches high in a single square meter. In deeper soils 

 of talus slopes it becomes a bushy plant, sometimes more than a 

 foot in height. 



In the scab-lands especially, Plantago purshii characterizes 

 large areas with its leaden color. 



The following plant lists include those especially characteristic 

 of this community : 



. 

 Composition of the Poa-Polygonum Associes 



Dominant Species (Consocies) 



Plantago purshii Polygonum majus 



Poa sandbergii 



Principal Species 



Antennaria dimorpha Eriogonum heracleoides 



Antennaria luzuloides Epilobium paniculatum 



Clarkia pulchella Festuca pacifica 



Cogswellia grayi Madia exigua 



Cogswellia gormani Madia glomerata 



Secondary Species 



Agoseris heterophylla Allium acuminafum 



Ago sens grandiflora Alsine nit ens 



