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 purshit 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 purshu Polygonum majus 
Poa sandbergis 
Principal Species 
Antennaria dimorpha Eriogonum heracleoides 
Antennaria luzuloides Epilobium paniculatum 
Clarkia pulchella Festuca pacifica 
Cogswellia grayi Madia exigua 
Cogswellia gormant Madia glomerata 
Secondary Species 
Agoseris heterophylla Allium acuminatum 
Agoseris grandiflora Alsine nitens 
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