ECOLOGY. 403 



gation of the grassland formation in northern Arizona, northern and 

 eastern New Mexico, and northern Texas has revealed tall-grasR 

 dominants wherever protection from grazing has existed, and leaves 

 no question that the short-grass plains are mixed prairie greatly changed 

 by overgrazing. 



Extensive study has likewise revealed a closer relationship between 

 the other associations of the grassland formation than was thought to 

 exist. Stiya comata and Koeleria cristata are found to be important 

 if not regular dominants of the original bunch-grass prairie, as well 

 as of the mixed prairie. Stipa pennata belongs in the desert plains 

 as well as in the mixed prairie, and Bouteloua racemosa was once as 

 common in the southern mixed prairie as it is to-day in the subclimax 

 prairie or the desert plains. Moreover, such typical dominants of the 

 subclimax prairie as Andropogon furcatus, A. nutans, and Elymus cana- 

 densis are found in abundance with true mixed-prairie dominants on 

 the foothills of Colorado, indicating the close relationship of these two 

 associations. The evidence of relationship obtained from distribu- 

 tion is confirmed by that from phylogeny, which strongly indicates 

 that the five grassland associations owe their present differentiation 

 to the dry phase of a grand climatic cycle extending backward into the 

 Pleistocene. 



In the case of the scrub formations, it now appears altogether cer- 

 tain that the climax area of each is much smaller than that indicated 

 by the presence of the characteristic dominants. Considerable atten- 

 tion has been given to determining the limits of the sagebrush and 

 desert scrub climaxes and of the broad ecotone of savannah that sepa- 

 rates them from the grassland. The actual sagebrush climax appears 

 to be restricted to Utah, Nevada, and trans-Sierran California, while 

 the focus of the desert scrub climax is in the Mohave and Colorado 

 Deserts and adjacent Mexico. In the case of chaparral, particular 

 attention has been paid to tracing the ecotone between it and the 

 coastal sagebrush in California and to determining the relations of 

 these two scrub associations to the bunch-grass prairie. The cedar- 

 pinyon woodland and the forest formations have been studied chiefly 

 with respect to the succession of the dominants and to the formation 

 of natural parks and savannahs. 



Natural Parks and Savannahs, by F. E. Clements and E. S. Clements. 



The nature and origin of natural park and savannah have again 

 been investigated throughout the West. The regions concerned were 

 the Manzanita Mountains of New Mexico, the Rocky Mountains of 

 Colorado and Wyomhig, the Blue and Cascade Mountains of Oregon, 

 the Sierra and Coast ranges of California, and the mountains of 

 northern and central Arizona. In all of these occur natural parks of 

 the two fundamental types, namely, those due to primary succession 



