iio A Study of the Vegetation of 



the fall of the year and tumbling over the ground, is piled by the 

 wind into great heaps on the leeward slopes of the hills. 



Westward, in the drier regions, and especially in the scab-lands, 

 Sisymbrium altissimum, locally known as Jim Hill mustard, from 

 its introduction along the right of way of the railroads, is pres- 

 ent to a degree almost unbelievable. Hundreds of acres in the 

 scab-lands are literally " taken " by this weed. From dwarfed 

 specimens a few centimeters high on the scab-rock, it ranges to 

 rank growths 'in the moist soil. It is a bad weed in the wheat 

 fields throughout the greater part of the region. 



The tar weed, Amsinckia intermedia, is likewise a troublesome 

 weed along roadsides and especially in wheat fields. South of 

 Snake River it is very abundant. Its dense coat of long bristly 

 hairs upon drying becomes extremely annoying to both men and 

 horses. 



Westward and especially in the slightly alkali regions the Rus- 

 sian thistle, Salsola kali tenui folia, and the Australian salt bush, 

 A triplex semibaccata, are often abundant. 



Dipsacus sylvestris, introduced a number of years ago, has 

 spread very rapidly and in many localities assumes the role of a 

 very thrifty and very obnoxious weed. 



The little geranium, Erodium cicutarium, is an introduced 

 weed which has become very common in gardens, feed lots, and 

 waste places. Often associated with it are Sanguisorba annua, 

 Geranium pusillum, and Verbascum thapsus. 



Common roadside weeds of especial abundance are Madia 

 glomerata, Marrubium vulgare, and the rattle grass, Bromus 

 brizaeformis. The absence of most roadside weeds so common in 

 the eastern and central states is very characteristic. 



About the numerous grain-loading stations throughout the 

 region many ruderals are gaining a foothold. Here the cars are 

 swept out and the seeds of various plant species scattered. 

 Among other weeds thus recently introduced, and which I have 

 seldom seen elsewhere, may be mentioned Ambrosia trifida, A. 

 psilostachya, Melilotus alba, M. officinalis, Cirsium arvense, Iva 

 xanthifolia, Datura tatula, and Datura stramonium. The prob- 

 lem of grain warehouses as centers of weed distribution would 



no 



