TREES OF NORTH AMERICA 



XXII. ROSACES. 



Trees, shrubs and herbs, with watery juices, terete branchlets, scaly buds, and alternate 

 leaves (opposite in Lyonothamnus), with stipules. Flowers perfect; calyx 5-lobed; petals 5 

 (0 in Cercocarpus), imbricated in the bud, inserted with the numerous distinct stamens on 

 the edge of a disk lining the calyx-tube; anthers introrse (extrorse in Vauquelinia), 2-celled, 

 the cells opening longitudinally; ovary superior in Lyonothamnus and Heteromeles, often 

 partly superior in Amelanchier; ovules 2 in each cell (1 in Cowania and Cercocarpus, 4 in 

 Lyonothamnus), anatropous. Seeds without albumen (albuminous in Lyonothamnus and 

 Cowania) . A family of about ninety genera chiefly confined to the temperate parts of the 

 world and producing many of the most valuable fruits, including the apple, pear, quince, 

 strawberry, raspberry, and blackberry. The six tribes into which the genera of the family 

 are grouped, have arborescent representatives in North America. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT GENERA. 



Tribe 1. SPIR^OIDE^:. Fruit a woody capsule. 



Flowers in terminal cymose corymbs; calyx-lobes persistent; ovary 5-celled; ovules as- 

 cending; mature carpels adherent below and opening down the back; albumen 0; leaves 

 simple. 1. Vauquelinia. 



Flowers in terminal corymbs; calyx-lobes deciduous; ovary 2-celled; ovules 4 in each 

 cell, pendulous; mature carpels opening on the ventral and partly on the dorsal suture; 

 albumen thin; leaves opposite, simple or pinnately divided. 



2. Lyonothamnus. 

 Tribe 2. POMOIDE^E. Fruit a pome composed of the thickened and succulent calyx- tube 



inclosing the papery or bony carpels; stipules free from the petioles. 

 Mature carpels papery. 



Carpels as many as the styles. 



Flowers in few-flowered terminal racemes on short spur-like lateral branchlets; ovary 

 3-5-celled; styles more or less united below; leaves simple; winter-buds small. 



3. Malus. 



Flowers in broad compound terminal cymes; ovary 2-4, usually 3-celled; styles 

 distinct; fruit subglobose; leaves unequally pinnate; winter-buds large. 



4. Sorbus. 



Flowers in large terminal corymbose panicles; ovary nearly superior, 2-celled; 

 styles distinct; fruit obovoid. 5. Heteromeles. 



Carpels becoming at maturity twice as many as the styles; flowers in erect or nodding 

 racemes; ovary inferior or partly superior; styles 2-5, more or less united below; 

 fruit subglobose or pyriform; leaves simple, deciduous. 6. Amelanchier. 



Mature carpels bony; flowers in terminal cymose corymbs; ovary 1-5-celled; styles dis- 

 tinct; fruit globose to pyriform; leaves simple, deciduous. 7. Cratsegus. 

 Tribe 3. DRYADS. Calyx-tube turbinate, campanulate or hemispheric; petals 5; ovary 

 composed of 1 or several carpels; fruit an akene tipped with the elongated plumose 

 style. 



Flowers terminal on short branchlets, solitary; calyx-tube turbinate; carpels 5-12; leaves 



alternate, toothed or pinnatifid. 8. Cowania. 



Tribe 4. CERCOCARP^E. Calyx-tube salver-shaped; petals 0; ovary composed of a single 



carpel; fruit an akene, tipped with the elongated plumose style. 



Leaves alternate, simple, entire or serrate. 9. Cercocarpus. 



Tribe 5. PRUNOIDE^E. Fruit a 1-seeded drupe; ovary 1-celled; style terminal; ovules 

 pendulous. 

 Flowers in fascicled umbels, or racemes; leaves simple, deciduous or persistent. 



10. Prunus. 



