22 FLOEA OF THE YELLOWSTONE NATIONAL PARK. 



THE GRASSES. 



The open areas of the Park, up to 9000 feet alt., are covered 

 with a luxuriant growth of the most nutritious grasses, the pre- 

 dominant species being mainly those known as " bunch grasses." 

 None of the so-called " buffalo " or " grama grasses," Buckloe, 

 Bouteloua, etc., are found. In all about seventy species are 

 known, but only about half of these enter to any extent into the 

 composition of the grass areas. 



Over the dryer portions, up to 7000 feet alt., the following are 

 the common forms, and of these the Stipas, Agropyrums and 

 Poa tenuifolia form at least 80 per cent. 



Stipa viridula, Trin. 

 Stipa comata, Trin. and Rupr. 

 Agrostis scabra, Willd. 

 Koeleria cristata, Pers. 

 Melica spectabile, Scribn. 

 Poa tenuifolia^ Buckl. 

 Bromus breviaristatus, Buckl. 

 Agropyruin divergens, Nees. 

 Agropyrum caninum, L. 

 Elymus Sitanion, Schultz. 



At still higher altitudes, or in more moist situations, will be 

 added Deyeuxia Canadensis, Beauv.; D. neglecta, Kunth.; Trise- 

 tum subspicatum, Beauv.; var. molle, Gray^ Poa Nevadensis, 

 Vasey ; P. memoralis, L.; Bromus Kalmii, Gray; B. ciliatus,*L.; 

 Deschampsia csespitosa, Beauv. The characteristic species of 

 moist meadows and bogs is Poa Nevadensis in various forms. 



Gradually many of the common species of the lower and 

 dryer areas disappearing being replaced by others until at about 

 8500 feet alt. We find an abundant, but in many respects, quite 

 distinct flora, beyond which point there is a decrease both in 

 luxuriance and number of species. 



