448 



The Thorn Trees 



Nutlets usually 2 to 4; leaves half-leathery, bright green and 



shining above. 

 Nutlets usually 2 or 3. 



Fruits, corymbs, and leaves hair}'. 



Fruits, corymbs, and leaves smooth. 

 Nutlets usually 3 or 4. 

 C. Nutlets with distinct cavities on their inner faces. 



Nutlets usually 2 or 3, with i deep cavity on each inner face; fruit 



red; leaves hairy beneath, at least along the veins, often hairy 



above; spines 3 to 10 cm. long; corymbs hairy, many-flowered. 

 Fruit subglobose to short-oblong, dark red; flesh succulent; 



leaves leathery, dark green and shining above. 

 Fruit pear-shaped to oblong, crimson; leaves thin, dull green, 



hairy, and with impressed veins above. 

 Nutlets with several shallow cavities on each inner face; fruit black, 



short-oblong to subglobose; nutlets 3 to 5, ear-shaped, with a 



conspicuous caly.x-scar; leaves smooth beneath, half -leathery; 



spines i to 3 cm. long. 

 Leaves broad; corj'mbs hairy. 

 Leaves narrow; corj'mbs smooth. 



Leaves lanceolate-elliptic; nutlets usually 4. 



Leaves small rhombic-elliptic; nutlets 5. 



44. C. pertomentosa. 



45. C asperijolia. 



46. C. Brainerdi. 



47. C. macracantha. 



48. C. Chapmani. 



49. C. Douglasi. 



50. C. rividaris. 



51. C. saligna. 



I. HAWTHORN Crataegus Oxyacantha Linnaeus 



This common species of the Old World has sparingly escaped from cultivation 



along roadsides and in thickets in the east. It 

 is a shrub or a small tree, sometimes 6 meters 

 high, with ascending or nearly erect branches 

 forming an oblong crown; the bark is dark 

 brown and scaly ; the twigs are reddish brown, 

 smooth, often end in spines, and are armed 

 with sharp chestnut-brown spines i cm. long 

 or more. 



The leaves are ovate, 3-lobed to 7-lobed 

 or cleft, toothed or doubly toothed, with small, 

 flattened teeth, i to 4 cm. long, i to 4.5 cm. 

 wide, sHghtly hairy or nearly smooth when 

 young, becoming smooth, except on the 

 lower side of the veins when mature, dark 

 green on the upper surface, paler beneath, 

 pointed at the apex, wedge-shaped, often ab- 

 ruptly so at the base; leaf-stalks 5 to 20 mm. 

 long. The flowers are white or pink, about 15 mm. wide, numerous in smooth 

 corymbs; the calyx-lobes are triangular, rounded or pointed; stamens about 20; 

 anthers pink; styles 2 or 3. The fruit ripens in October, is globose or subglobose, 



Fig. 390. Hawthorn. 



