PRAIRIE PLANTS OF SOUTHEASTERN WASHINGTON 277 



The roots, which are a dirty-gray in color, resemble those of 

 Agropyron but taper down faster, and have finer laterals which 

 branch mostly to the third order. These laterals, like those of 

 the shallow rooted Poa, are more numerous than in Agropyron. 

 Six plants were examined. The deepest root found was at 28 

 inches, and 15 inches was determined as the average maximum 

 depth. 



Balsamorhiza sagittata {Fig. 12) 



The balsam root is, with the exception of Agropyron spicatum 

 and Festuca ovina ingrata, the most characteristic plant of the 

 high prairies of eastern Washington. 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 

 4 square meters. Only on the steeper northeast slopes and wet 

 valleys is it absent. A medium sized mature plant occupies 

 an area of 4-5 square feet, may have as many as 50-80 of the 

 large sagittate leaves, and a total leaf surface of 30 square feet. 

 From the short, thick, multicipital stem (I have counted 39 

 individual shoots on a stem 9 inches in diameter) the new leaves 

 appear in April. By the first of May the plant is often in full 

 bloom and is the most conspicuous member of the vternal aspect 

 which lasts until about June 1st. After this the whole aerial 

 part dries up, but the dead leaves are conspicuous throughout 

 the year. 



Twenty-five root-systems were excavated and examined. 

 Balsamorhiza has a tap root sometimes reaching a diameter of 

 4 inches and an extreme depth of 8 feet and 10 inches. The 

 laterals seldom come off in the first 6 inches of soil, but below 

 this numerous strong laterals occur, sometimes 1 inch or more in 

 diameter, and these often run rather horizontally for 2 or 3 feet 

 before they turn downward. They may ultimately reach depths 

 of 5 feet or more. The lateral branching is profuse, and in all 

 directions the soil is laid hold upon. Sometimes the tap splits 

 up into nearly equal parts at a depth of a few feet. The tip of 

 the tap root is often dead, and, if alive, never much branched. 

 Small branch orders near the tip are not abundant. The older 



THE PLANT WORLD, VOL. 18, NO. 10, 1915 



