NO. 2 gentry: land plants 81 



CALIFORNIA GULF REGION 



General Physiography 



The California Gulf Region possesses considerable physiographic 

 unity, although its boundaries are not fast. For the purpose of this study 

 it includes, besides the great gulf nucleus itself and its chromosomic 

 islands, the surrounding coastal plains, mostly narrow and in part lack- 

 ing, the coastal mountains, and the Cape District of the peninsula. It 

 forms a long narrow area nearly 1000 miles long containing about 

 150,000-175,000 square miles. It is nearly co-extensive with the Sonoran 

 Desert, the latter comprising additional area in northern Sonora, south- 

 eastern California, southwestern Arizona, and on the peninsula except 

 in the Cape District. The western middle portion of the peninsula is 

 being considered in another study. 



Nearly half the area is occupied by the sea. Its western shores are 

 generally precipitous and without rivers, while its eastern are mostly 

 low coastal shores with several intermittent rivers. From the mouth 

 of the Colorado River in the apex, the gulf gradually deepens to 2600 

 meters under its 225 kilometer-wide mouth. The upper part of the 

 gulf is generally less than 300 meters in depth with low gradients on 

 the eastern and northern margins. South of Angel de la Guardia and 

 Tiburon Islands it rapidly deepens to over 1000 meters and the 1500 

 meter contour comes well up into the gulf. In this water are 25 to 30 

 larger islands and many smaller ones, some of which are no more than 

 jagged rocks set upon by the tides and wind-driven waves. The topo- 

 graphy of the northern half is terrestrial in type rather than marine. 



It is the water relations, both of the sea and of the air, that give 

 the country its distinctive quality. The gulf water is changeful. It can 

 be as quiet as a forest pool at dawn or as choppy as Lake Erie. High 

 seas often run under the strong and recurrent winds. In the late sum- 

 mer of the convectional storm cycle, hard squalls suddenly appear and 

 have upset many a light ship, and in the early colonial days made the 

 passage of the gulf and the colonization of the peninsula a hazardous 

 undertaking. The waters teem with life ; fish, shrimp, whale, and many 

 other animals run in and out in their seasons, as also do a vast assem- 

 blage of birds over the surface; others, from plankton and crabs to 

 sharks and turtles, are permanent residents. The sublittoral zone is 

 covered with an abundance of varied algae. Under the brilliant sun- 

 light, the ever mobile waters, blue or green or vermilion or gray, are 

 set sharp against the rocky, uneven, and disconsolate shores. 



The water of the air is rare, because it seldom falls as rain, although 



