82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 13 



actually the hot air contains more moisture than usually exists over 

 temperate regions. Hence, in contrast to the dense biota in the sea, the 

 land is relatively barren. The land biota, though seemingly dead, is 

 nevertheless there, and with many special adaptations for survival of 

 drought. When rains fall, the plant life suddenly becomes intensely 

 active and the land becomes green and flower-colored. To the man who 

 may be there the desolate then becomes a garden of well-spaced forms. 

 And it, too, in brilliant sunshine is set sharp against the inanimate rocks 

 beside the waters of the gulf. Such is the impression of the gulf region 

 on the senses today. Geologically, the perception has quite a different 

 quality, because the eye and mind are removed from the object by many 

 milleniums. 



In spite of changeful orogeny, the California Gulf Region has had 

 a persistent character since the early Mesozoic. The gulf itself is a de- 

 pressed block, which Schuchert (1935), has discussed as a part of the 

 southern Pacific geosyncline. This sea-invaded trough has had a strik- 

 ing physiographic evolution, the remarkable events and character of 

 which are geologically revealed at every great turn. The biota of the 

 lands has had a restless place and has endured displacements, inunda- 

 tions, extinctions, and has been forced into migrations with the coming 

 and going of the sea, with the submergence or emergence of mountains, 

 and with the concomitant changes of local climate. Close study of the 

 plant and animal life, when directed by a correlating intelligence, should 

 reveal a course of evolution, expressed jointly by plant and rock, hardly 

 equaled in plant geography. There is some lack of agreement among 

 geologists regarding the history of the gulf region, primarily because 

 investigations are still in preliminary stages. From the reconnaissance 

 work that has been done, however, the general history can be outlined. 

 Schuchert has been foremost in synthesizing available knowledge and 

 I have drawn heavily upon his great work in the following paragraphs. 



Judging from the world-wide deposits of fossil plants, the modern 

 angiosperms had their inception in the Upper Mesozoic, following the 

 biota dominated by such groups as the seed ferns, the cycads, and the 

 saurians. When the Tertiary opened, the majority of the modern plant 

 families and genera were pretty well established. Hence, in seeking the 

 origin of the desert flora of the gulf region we are concerned with 

 events in the Cretaceous and onward. Of all the major floral elements, 

 the desert floras are the most obscure in origin. They are almost un- 

 represented in the fossil record. We must seek other sources of evidence 

 for determining their origin, their migrations, and their growth. A 



