THE OLIGOCENE-MIOCENE CLISERE. 



367 



the Eocene, while grassland climaxes must have been much more widespread. 

 The coseres of this cycle are represented by the lignite beds of the Brandon 

 formation of the Atlantic. Much more remarkable, however, are the frag- 

 mented volcanic coseres of the Yellowstone and elsewhere. These contain 



Fig. 35. — Costase of forest climaxes buried by volcanic ejecta. Specimen 

 Ridge, Yellowstone Park. After Knowlton. 



of course only the climax or climax stages of the sere, but they are unique in 

 the large number of successive horizons. The number of stases varies but 

 the formation at Specimen Ridge shows 12 to 15, forming a costase 2,000 feet 

 thick (Knowlton, 1914:8). The dominants were redwoods (Sequoia) and 

 pines {Pitoxylon), though Juglans, Hicoria, Fagus, Acer, Platanus, etc., made 



