278 The Oaks 



by insect punctures on some species, the best containing from 60 to 70 per cent, 

 of tannic acid. These galls and some of the barks are valued as astringents in 

 medicine. The thick corky bark, especially of Q. Suber Linnaeus, and of Q. 

 occidentalis J. Gay, both natives of southern Europe, is valued as the material 

 from which corks and many other useful articles are manufactured. The nuts of 

 many species have been used from time to time as food for man and are still so 

 used in some districts, especially in the mountains of Mexico; roasted they also 

 form a substitute for coffee. The Old World species, Q. Robur Linnaeus, in 

 its several forms, is extensively used in Europe as an ornamental shade tree, and 

 is planted to some extent in this country. 



They have altemate, simple, deciduous or persistent leaves, which are pin- 

 nately lobed, variously toothed or entire, often bristle-tipped. The stipules usually 

 fall off early. The flowers are monoecious, the staminate numerous, usually in 

 clustered slender drooping catkins, their calyx bell-shaped, 4- to 7-lobed, subtended 

 by caducous bracts; stamens 6 to 12, usually exserted; filaments thread-like; 

 anthers usually oblong and smooth, sometimes hairy; rarely there is a rudimentary 

 ovary. The pistillate flowers are soUtary or in small clusters; calyx um-shaped, 

 joined to the usually 3-celled ovary and subtended by a many-bracted involucre; 

 ovules 2 in each cavity, usually only one maturing; styles usually 3, stigmatic 

 tipped. The fruit, called acorn, consists of an indehiscent, i-celled, usually 

 i-seeded, leathery, ovoid, oblong or subglobose nut, more or less embraced by a 

 cup consisting of the enlarged involucre of imbricated and somewhat enlarged 

 bracts; cotyledons half round, occasionally imited. The fruits of many of the 

 species require two years to mature. 



The name is the old classic name of the oak, probably of Celtic origin and 

 signifying beautiful tree, the type species being the European Quercus Robur 

 Linnaeus. 



In addition to the arborescent species, there are a considerable number of 

 shrubs, especially in the region of the Rocky Mountains and beyond. 



A. Leaves or their lobes mostly bristle-tipped; styles elongated; shell of 



nut mostly pubescent inside, 

 a. Fruit maturing the second season. 

 * Leaves deciduous. 



t Leaves pinnatifid or pinnately lobed, or, if entire, obovate or 

 spatulate. 

 I Leaves pinnatifid or pinnately lobed, usually deeply so. 

 "Leaves green on both sides. 



Cup saucer-shaped, much broader than high. 

 Cup 16 to 30 mm. broad; leaves dull, not shining. i. Q. rubra. 



Cup 8 to 16 mm. broad; leaves shining above. 

 Nut little, if at all, longer than thick. 

 Petioles 2 cm. long or more; leaves 5- to 9-lobed. 2. Q. palustris. 

 Petioles less than 2 cm. long; leaves 3- to s-lobed. 3. Q. georgiana. 

 Nut ovoid, considerably longer than thick. 4. Q. Schneckii. 



Cup top-shaped to hemispheric or deeper. 



