OAKS OF PACIFIC SLOPE. 153 



Southward the species increase to ten in southern New England, while 

 the gulf states contain some nineteen species; but the central eastern 

 portion of the Mississippi Valley contains more individual trees to 

 the acre and they attain the largest size there than elsewhere in 

 America. 



Leaving the prairies and approaching the high, dry, and cold mid-' 

 continental plateaus, the oaks even the dwarf varieties are almost 

 entirely absent. 



PACIFIC SLOPE A UNIQUE REGION. 



The Pacific slope of North America comprises, of course, all that 

 part of the continent west of the Rocky Mountains; but for the pur- 

 pose of this paper, only the American portion north of the Mexican 

 boundary will be considered. This region includes two territories, five 

 states, and a portion of three others. It happens that this large region, 

 owing to the continuity of the high Rocky Mountain range without a 

 break or low pass from the Arctic Ocean to the Gulf of Tehuantepec 

 is possessed of a practically distinct flora. Not a pine, spruce, fir, 

 cedar, or cypress, not an oak, ash, walnut, or maple of the Pacific slope, i& 

 identical with those beyond the Rockies. So we have here a compact, 

 definite, and nearly special creation. 



Because the Mexican boundary is not a high mountain range, but 

 only a straight surveyor's line across a continuous plateau, the floras 

 of Mexico and the United States commingle here, five Mexican oaks 

 dripping over the line into New Mexico and Arizona. Three local 

 species arise there, too, sharing the highlands with them; but from 

 thence northward, inhabiting the humid, forcing climate of California 

 and Oregon, to Washington and British Columbia, the thirteen speciea 

 are all our own, the largest and noblest of them being in the great 

 valley of California. 



PRINCIPAL PUBLICATIONS OF AMERICAN OAKS. 



"Sylva of North America," a fine quarto volume, was published 

 1817, by Andrew Michaux, as the result of the explorations of h- 

 father and himself in the then little-known region of America. It 

 contains descriptions with excellent colored plates of the foliage and 

 fruit of twenty-six species of oak inhabiting the region east of the 

 Mississippi River. The continuation of the Sylva, 1857, by Thos Nut- 

 tall, added four more, all from the Pacific slope; Quercus agrifolia, 

 our first-discovered, storm-beaten live oak; Q. lobata, the noble valley 

 oak; Q. Garryana, the fine Pacific white oak; and Q. dumosa, the low, 

 bushy scrub oak, or chaparral. 



"The Oaks of the United States," a scholarly paper, read 1876 



