20 OUTLINE OF PLANT GEOGRAPHY 



save by the Indians and buffalo, are now the granaries of the 

 nation. 



The deserts and mountains of this far west have as yet changed 

 but little; but along the Pacific Coast the same changes are going 

 on as in the Atlantic states a hundred years ago. 



In California the great valleys are covered with fields of wheat, 

 barley and alfalfa; orchards and vineyards cover the foot-hills. 

 The climate permits the growth of many products of the warmer 

 zones, and oranges, olives, figs and lemons thrive, as well as the 

 apples, pears, cherries and plums of the north. 



In these far western states, where a long dry summer prevails, 

 irrigation plays an important role, and land naturally a desert 

 or semi-arid, yields rich crops when water is available. 



Much land in southern California, now covered with luxuriant 

 orange orchards, and adorned with innumerable beautiful trees 

 and shrubs brought from distant countries, was desert before the 

 days of irrigation. 



California, it is true, much more than a century ago, had in- 

 troduced from Spain the orange, grape and olive, which flourished 

 there long before it became a part of the United States. 



Besides the economic plants introduced by man he has imported 

 from all over the world a host of ornamental species which adorn 

 his gardens. Sometimes these escape from cultivation and become 

 quite naturalized. In the cool moist coastal regions of northern 

 California and Oregon one meets the showy broom and foxglove 

 of Europe — and one sees these same plants in the similar climates 

 of central Chile and New Zealand. In the latter country the 

 sweet briar and blackberry, introduced from England as garden 

 plants, have escaped and become extremely troublesome weeds. 



Most plants ranking as weeds, however, have been introduced 

 accidentally, and wherever man has migrated, weeds have fol- 

 lowed him, or been imported from divers sources. Many of the 

 worst weeds owe their rapid dissemination to specially favorable 

 adaptations for seed dispersal, like the wind-borne seeds of thistles 

 and dandelions, or the hooks of burdocks and cockle bur, which 

 stick to the coats of animals or men. 



Weed seeds may come in mingled with seed grain, or in the dirt 

 adhering to animals or in the cargo of ships and railways. Rapid 

 transit for mankind furnishes equally quick transport for these 



