348 TREES OF NORTH AMERICA 



XXI. ROSACEiE. 



Trees or shrubs, witli watery juices, terete braiiclilets, scaly Imds, and alter- 

 nate leaves {opposite in Li/oNotha?n/iits), with stipules. Flowers ])erfect ; calyx 

 5-lobetl ; petals 5 {0 in Cercocarj)i(s), 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 gartly superior in 

 Amelanchier ; ovules 2 in each cell {1 in Cercocarjnis, Jf in Lyonothamnus), 

 anatropous. Seeds without albumen {alhnminous in LyonothaTiinus). 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. Of the six tribes into which 

 the genera of the family are grouped, five have arborescent representatives in 

 North America. 



CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT GENERA. 



Tribe 1. Spir^OIDE^. Fruit a woody capsule. 



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

 ascending ; mature carpels adherent below and opening- down the back ; albumen ; 

 leaves simple. 1. Vauquelinia. 



Flowers in terminal cymose 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^. 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 simple terminal cymes 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 larg-e. 



4. Sorbus. 

 Flowers in larg-e 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 nod- 

 ding 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-eelled ; styles 

 distinct ; fruit globose to pyriform ; leaves simple, deciduous. 1. Crataegus. 



Tribe 3. CERCOCARPEiE. Carpels free from the persistent calyx, becoming akenes. 



Flowers axillary, solitary ; petals ; ovary 1 or rarely 2-celled ; ovule 1 ; fruit tipped 

 with the elongated persistent plumose style ; leaves simple, persistent. 



8. Cercocarpus. 

 Tribe 4. Prunoide^. Fruit a 1-seeded drupe ; ovary 1-celled ; style terminal ; ovules 

 pendulous. 



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



9. Prunus. 



