152 PACIFIC STATES FLORAL CONGRESS. 



ground to the exclusion of predecessors and newcomers. The oak thus 

 replaces the pine, to the surprise of some observers, and continually, 

 as the pine forests of the eastern states are cleared away, the rugged 

 black oaks, often the little, worthless scrub oaks, seize upon the 

 dominions. 



Forests of oak extend thus into the naturally treeless western por- 

 tion of the Mississippi Valley, reclothing the prairies and the partial 

 deserts, welcomed and protected by the settlers. The kind of oaks 

 that survive most in forests of many species is not, generally, the most 

 valuable, the white oak group, but the coarse-grained, usually worth- 

 less black oaks. And this is accounted for very readily; the bitter, 

 astringent qualities of the acorns of the black oaks are left by swine, 

 squirrels, and birds alike, to germinate, while they hunt industriously 

 for the sweet, nutritious acorns of the white oaks. 



VALUABLE PRODUCTS. 



The family of oaks, comprising the botanical genus of Quercus, is 

 distinguished, not only for their generous shade, owing to their usually 

 large and numerous leaves, but several of the arboreal species of 

 white oak are celebrated as timber trees. Of these the most valuable 

 in various manufactures are Quercus alba, the white oak of the north- 

 ern states, Q. virens, or live oak of the southern states, and the 

 Q. platanoides, or white oak of the middle western states, while others, 

 including the Q. densiflora, the tan-bark oak of the California coast, 

 are prized for the yield of bark collected by the ton annually for mak- 

 ing leather. One peculiar species, Q. suber, the cork-bark oak of 

 southern Europe and northern Africa, yields the soft, spongy bark 

 from which is derived the cork of commerce. Also from early times 

 oak galls caused by the punctures of insects, have been used for dye- 

 ing, for making ink, and, indeed, for wound-dressing and for medicine. 



DISTRIBUTION. 



While many species of oak are doubtless unknown, from the nature 

 of the regions they affect (the high, broken mountain slope's, mostly 

 unexplored), there have been discovered and described over three hun- 

 dred species. 



Europe has comparatively less than similar regions east and west 

 of it. The number in Xorth America north of Mexico already known, 

 is about fifty. The American species are mostly grouped in two 

 regions, the eastern Atlantic slope and the extreme western Pacific 

 slope. 



Of the eastern oaks three species the red oak, the bur oak, and the 

 white oak are found at the northern limit in northwest Ontario. 



