OKLAHOMA ACADEMY OF SCIENCE 83 



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XIII. FALL GRASSES OF CLEVELAND COUNTY^ 



OKLAHOMA 



C. W. Prier 



From Department of Botany, University of Oklahoma. 



Grasses are very widely distributed over the earth's surface. 

 The species are most numerous in the tropical regions, although 

 the plants are scattered and do not form such vast areas as is their 

 habit in the moist temperature regions. In regions of insufficient 

 moisture grasses form bunches which are more or less scattered. 



The family is called Poaceae by some authors but Britton and 

 Brown use the nme Gramineae which term is used throughout this 

 paper. A very large number of the Gramineae are cosmopolitan. 

 There are upwards of 3,500 species, th^s ranking fifth in point of 

 numbers among flowering plants, and are exceeded only by the 

 Orchidaceae among the Monocotyledons. The paramount import- 

 ance of the family is their great economical value in that they fur- 

 nish so many plants of commercial use to man. 



The separation of the family into subdivisions is a matter of 

 exceptional difficulty. In Gramineae more thn in any other family 

 the student is compelled to rely upon combinations of characters 

 rather than upon certain peculiar characters. No agrostologist, as 

 yet, has succeeded in establishing a more natural or more definite 

 division than Brown's original primary one into the two great 

 groups, Panicaceae and Poaceae, although many attempts have been 

 made. 



In "Genera Plantarum" by Bentham and Hooker the genera of 

 Poaceae are recorded as 289; the species as 3200. 



The number of genera now known is not far from 400 and the 

 number of species more than 3,500. Recent botanists are inclined to 

 increase the number of both genera and species. 



In the whole of North America there are about 150 native 

 genera comprising about 1300 species of which over 100 species 

 have been introduced, and among them are found some of our 



