The Origin of the Desert Climax and Climate 133 



There is almost no direct fossil evidence of the nature and 

 composition of the deciduous forest in the desert region during l^^ 

 the Tertiary. The nearest plant deposits of the Miocene are those 

 of Esmeralda in Nevada and Table Mountain in the central 

 Sierra, neither of them adequate to the purpose. The most satis- 

 factory flora is that of the Mascall (Chaney, 1925; cf. also Berry, 

 1929) ; how^ever, for the most part this lies 7 or 8 degrees to the 

 north and the species must have been much changed or reduced 

 so far to the south. The fauna of the Mascall is thought by Mer- 

 riam and Sinclair (1907) to denote open forest and savannah, 

 while that of the Barstov^ indicates an open well-grassed country 

 (Merriam, 1919:450). The presence of Quercus agri folia in the 

 Pleistocene of La Brea and the Pliocene of Ricardo is suggestive 

 only of savannah such as occurs today through the southern half 

 of cismontane California. 



The conclusions to be drawn from transads are more satis- 

 factory in respect to the nature and composition of the forest, but 

 are less clear in respect to time. The transads of Juglans, Acer, 

 Platanus, and Fraxinus indicate the probability that these were 

 associated with the existing willows and cottonwoods as late as 

 the wet phases of the Pleistocene and through most of the Pli- 

 ocene. However, with the aid of indices drawn from adjacent 

 fossil floras, regional faunas, and from climatic correlations, it is 

 possible to reconstruct climaxes and postclimaxes that may serve 

 as useful working hypotheses. During the wetter portions of the 

 glacial period, there was probably woodland along the valleys, 

 on broken ridges, and in sandy tracts, composed of Quercus agri- 

 folia, dumosa, douglasi, and Arbutus, Aesculus, and Primus, but 

 the evidence of grazing animals suggests that these did not form 

 a climax even as early as the Miocene. This view is confirmed by 

 the Mascall, which grew in a cooler, more humid climate. 



