18 CALIFORNIA GARDEN FLOWERS. 



flow downward over its western or southern slopes. These winds 

 are hot and dry, or cold and dry, according to the season of the year; 

 as they traverse snow fields in winter and sun-baked plains in summer, 

 before entering the area of California. 



Opposite in direction, source and character are the southerly winds 

 of the rainy season which bring ocean temperatures from the south- 

 west while the storm-centers advance from the north, according to 

 the cyclonic movement of storms. 



All of these and other general phenomena, together with more 

 localized phenomena of down-flow ,and up-rise of air, according to its 

 temperature, and other conditions of frost occurrence, the times and 

 amounts of rainfall, the force of the winds and their content of 

 moisture vapor all these are influenced or determined by topography 

 as involved in elevation, exposure, and relation to adjacent features 

 of environment and are to be expressed in terms of plant growth 

 through experience. 



Certain Plants May Define Our Climatology. It seems possible 

 that at some future time the vast and varied area included in the state 

 of California may be subdivided or districted by the success or failure 

 of certain plants, according to a scheme of life-zone. This has in 

 fact been proposed and entered upon with indifferent success thus far 

 because the exotic plants included in the effort were distributed largely 

 by commercial impulse to grow them and therefore the use of them 

 as standards of natural suitability went .astray. Though the observed 

 thrift of a plant might 'be demonstrated, the absence of another plant 

 might be rather due to unprofitability than to lack of adaptation. Nor 

 does the botanical scheme of distribution serve the plant grower any 

 better purpose for wild plants are often very safely carried beyond 

 their chosen habitats by horticultural arts of irrigation or protection. 

 Still it is possible that at some future time some one may gain posses- 

 sion of enough knowledge of plant requirements and of gardening 

 arts to produce a horticultural map of California which will designate 

 districts of actual and potential equivalence more intelligibly than 

 they can be expressed in isobars and isotherms. And yet it may be 

 expected that these lines will approach meridians of longitude rather 

 than parallels of latitude, just as our isobars and isotherms do, because 

 our climatic equalities run roughly northward and southward, as do 

 the coast line and the mountain ranges which are factors in their 

 production. 



Elevation and Ocean Influence. The two regulating factors in a 

 local climate seem to be elevation (both above sea-level and adjacent 

 plains) and modification of ocean influence by distance or by inter- 

 vention of great barriers. If it were simply a matter of elevation, 

 contour lines would easily define our districts but lines of adaptation 



