SS OUTLINE OF PLANT GEOGRAPHY 



proximity to the coast, or the effects of large inland bodies of water 

 like the Great Lakes. 



In the western mountain area, however, topography exercises 

 a very great effect on the climate, largely controlling both tempera- 

 ture and precipitation. The direction of the mountain ranges, 

 as well as their height, strongly influences the amount of precip- 

 itation, and also the temperatures of the adjacent regions. This 

 is very plainly shown in many places on the Pacific Coast, Where 

 the mountain ranges are parallel with the coast, as in central 

 California, the moisture is mainly precipitated on the windward 

 (west) side, and inland the climate is much drier. This difference 

 in the rainfall within a short distance may be very great. Thus 

 in the canyons of the Santa Cruz mountains within 25 miles or 

 less of Stanford University, the rainfall may average more than 

 60 inches annually, and a forest of giant redwoods clothes the 

 mountain sides; while at the University, in the valley to the east 

 of the mountains, the rainfall rarely reaches 20 inches, and the 

 open valley supports only scattered tree growth. 



The inland valleys, too, shut off from the cool ocean breezes, 

 have very high temperatures compared with the cool coastal sum- 

 mer climate. While San Francisco during July and August rarely 

 sees the thermometer reach 70°, the inland cities like Fresno may 

 have maxima exceeding 110°. 



Eastern United States and Canada 



As in the Eurasian continent, there is not a very clear line of 

 demarcation between the sub-arctic zone and the north temperate. 



Along the Atlantic coast temperate conditions prevail as far 

 north as New Brunswick and Nova Scotia, which in the parts 

 adjacent to the sea enjoy a much milder climate than prevails 

 elsewhere in eastern Canada, and a number of plants are found 

 here which are not met with again until the coast of New Jersey 

 is reached. It has been thought l that they are relics of an ancient 

 coastal flora which once occupied the now submerged continental 

 shelf. Perhaps the most interesting of these is a small fern, 

 Schizaea pusilla, the only representative in the United States of a 



1 Fernald, M. L., "The Gray Herbarium Expedition to Nova Scotia," Rhodora, 

 Vol. XXIII, May, 1921. 



