FAGACEAE 



The Oaks 

 Characteristics of the Genus Quercus L. 



HABIT. Deciduous or evergreen trees or shrubs; with as- 

 tringent properties; pubescence of fascicled hairs. 



LEAVES. Alternate; simple; deciduous or persistent; shape 

 and size often variable on same tree; stipulate. 



FLOWERS. Regular; monoecious; vernal; staminate in 

 clustered aments, individual flowers with a 4-7-lobed calyx 

 enclosing 6 (rarely 2-12) stamens; pistillate solitary or in 2 to 

 many-flowered spikes, individual flowers with a 6-lobed calyx 

 surrounding a 3- (rarely 4—5) celled ovary with 1-2 ovules 

 in each cell, the whole partly enclosed in an involucre. 



FRUIT. An acorn; 1 -seeded by abortion; maturing in 1-2 

 years; partially enclosed by scaly cup (modified involucre). 



TWIGS. Slender to stout; angled; pith homogeneous, stel- 

 late; marked by plate lenticels and semicircular lear scars. Win- 

 ter buds: clustered at end of twig; terminal present; with many 

 chestnut-brown scales imbricated in 5 ranks. 



BARK. Scaly or dark and furrowed. 



WOOD. Heavy; hard; strong; with prominent rays. 



SILVICAL CHARACTERS. Varying from intermediate in 

 tolerance (many white oaks) to intolerant (most red and live 

 oaks); long-lived; generally with deep taproot systems; hybrid- 

 izes frequently. 



GENERAL. This is a variable genus and it is often difficult 

 to distinguish between the species. Fifty-nine native species 

 are recognized as reaching tree size; in addition there are numer- 

 ous hydrids and varieties as well as many shrubby species. Five 

 shrubby southwestern forms that are reported to become small 

 trees in Texas, New Mexico, or Arizona are not keyed out. These 

 are Q. graciliformis Mull., Q. gravesii Sudw., Q. grisea Liebm., 

 Q. harvardii Rydb., and Q. laceyi Small. The key distinguishes 

 between the tree species and all oaks of importance are described 

 and pictured in more detail. The native oaks logically break them- 

 selves down into 2 subgenera, the white oaks and the red oaks, 

 each of which is further subdivided into 3 groups. A recent study 

 indicates that all the live oaks should be placed under the red 

 oak group on the basis of wood structure. 



The English oak, Quercus robur L. is commonly planted. This 

 oak has leaves which resemble white oak but are smaller (2^-5 

 inches long). It is further characterized by having the fruit borne 

 on peduncles 1-3 inches long. 



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