20 TREES AND FIjOWERS OF 



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GREASEWOOD 



Alder (Alrms) . Though the alder is not so abun- 

 dant in the Park as is the birch, it is still fairly fre- 

 quent in its occurrence, and has about the same distri- 

 bution. It does not grow quite so tall as the birch, 

 and the twigs are less slender and do not droop. The 

 bark is a duller brown, and the leaves are somewhat 

 larger and more coarsely toothed on the margins. The 

 fruiting bodies are very characteristic. They are 

 borne in clusters at the ends of the twigs, and their 

 dried remains hang on to the branch for a year or 

 more, instead of falling during the summer as do those 

 of the birch. They may also be distinguished by their 

 shorter and thicker form. 



Greasewood (Sarcobatus) . Though very abun- 

 dant on Western plains, greasewood is rare in the 

 Yellowstone Park, being found only in a few limited 

 spots near the Gardiner entrance. This is because 

 greasewood requires a high alkali concentration in the 

 soil, which is lacking in most places in the Park. The 

 plant is a low, somewhat spiny shrub, with gray bark 

 and very narrow, fleshy leaves of a livid grayish-green 

 color. They have also a decidedly salty taste. 

 Throughout the West, greasewood is regarded as a 

 sign of alkali soil, while sagebrush is considered a sign 

 of soil good for farming if water is available. 



