The Hop Trees 573 



ing above, paler beneath and abundantly black glandular-punctate. The perfect 

 flowers appear in April or May in finely hairy panicled cymes 2 to 5 cm. long, 

 axillary to the upper leaves. The calyx consists of 4 ovate, sharp-pointed sepals, 

 united at the base; the 4 petals are white, thick, oblong, 2.5 mm. long, blunt and 

 slightly crisped and spreading; stamens 4, shorter than the petals, their filaments 

 flattened and smooth; disk, ovary and style glandular-punctate, the 4-lobed ovary 

 depressed-ovoid. The samaras are in clusters of 3 or 4, oblong, 6 to 8 mm. long, 

 their wings ovate, rounded, 6 to 12 mm. long and netted-veined. 



The w^ood is hard, close-grained, orange to brown; its specific gravity is about 

 0.88; it is used for fuel. 



The genus consists of about 4 species, all American, occurring from Texas to 

 Paraguay, the type being H. PlcBana Tulasne of Colombia. The name is in 

 commemoration of Dr. Louis Theodore HeHe, a French physician. 



III. THE HOP TREES 



GENUS PTELEA LINNAEUS 



HIS wholly American genus, occurring from Canada to southern 

 Mexico, contains about 12 distinct species of shrubs or low trees of 

 no special economic value, though many more have been described. 

 They have alternate, rarely opposite, 3- to 5-foliolate leaves with- 

 out stipules. The polygamous flowers are greenish or yellowish on slender pedi- 

 cels, in terminal often compound cymes. The calyx is deeply divided into 3 to 

 5 lobes; petals 3 to 5, imbricated, longer than the calyx, spreading and deciduous; 

 stamens equal to the petals in number and alternate with them, their anthers 

 ovate, sometimes cordate, introrse, 2-celled and opening longitudinally; in the fer- 

 tile flowers, however, the stamens are shorter, with imperfect anthers; ovary 2- or 

 3-celled; style very short; stigma 2-or3-lobed; ovules 2 in each cavity, one above 

 the other, the upper one only becoming fertiHzed. Fruit a 2-celled, 2-seeded sa- 

 mara, orbicular or nearly so, with a broad reticulated wing; seed with a smooth 

 or slightly wrinkled leathery coating, and fleshy endosperm. 



The generic name is the ancient Greek name of the Ash, which the fruit was 

 thought to resemble; Ptelea trifoliala is the type species. 



Two of the species occurring in our area become arborescent. 



Leaflets lo to 15 cm. long, usually acuminate; fruit about 25 mm. across; 



eastern. i. p. trijoliata. 



Leaflets 2.5 to 7.5 cm. long, usually blunt at the apex; fruit 18 mm. across; 



Californian. 2. P. crenulala. 



