Southeastern Washington and Adjacent Idaho. 55 
The June grass, Poa sandbergii, one of the pioneers of herba- 
ceous vegetation in the moss consocies, is also perhaps one of the 
most important interstitial plants of the prairies. It grows in 
small tufts usually only about 0.5 to 1.5 inches in diameter but 
as many as 30 to 40 of these may occur in a single minor quadrat 
between the bunches of Festuca and Agropyron. It is called 
June grass because of its habit of flowering in May or early June 
and wemaining dormant until the advent of the fall rains. This 
means of evading drought is necessitated by its very shallow 
root-system, which seldom exceeds 8 inches. Its xerophytic 
tendencies are shown by its less abundance in mesophytic situa- 
tions. 
The sod-forming habit of Agropyron spicatum in the prairies 
of eastern Washington is in marked contrast to its well developed 
bunch habit on the rim-rock or in the shallower and drier soils 
westward. I have found the soil quite filled with rhizomes of 
considerable length connecting smaller clumps of this grass. 
It may well abandon this marked xerophytic character, for 
its long roots extend into the fourth and fifth foot of soil, and 
tap the earthen reservoir far below the root limits of competing 
grass species. 
Another common bunch-grass, which, with the three preceding, 
completes the list of dominant grass species, is Koeleria cristata. 
Like Poa, the bunches are often small, but numerous. It com- 
pletes flowering in early July and remains dormant until revived 
by the autumn rains. Its well developed but short root-system 
gets water from the first 15 inches of soil only. 
The entire absence of late blooming grasses, such as An- 
dropogon, Sorghastrum, Bouteloua, and others of the prairie- 
plains region, may be accounted for by the peculiar distribution 
of the precipitation. 
A most characteristic plant of the prairies, and one which for 
a time often outranks the grasses, is the prairie sunflower, Bal- 
samorhiza sagittata (Fig. 42). Its abundance, size, and duration 
all unite to make it a very important ecological species. It is not 
unusual to find a dozen of these plants in an area of four square 
meters. Only on the steeper northeast slopes and moist valleys 
55 
