98 American Midland Naturalist Monograph No. 4 



Rose Family (Rosaceae) 



The rose family as considered here is one of the largest of the families 

 represented in the national parks, at least as far as the shrubby species are 

 concerned. It also includes a large proportion of species with edible fruits. 

 The family is characterized by usually showy flowers or rarely with the 

 petals lacking. 



Field Guide to the Genera 



A. Plants low, creeping, mostly alpine ; flowering stalks erect, 



1 TO 9 inches tall. 



Flowers small, borne in dense oblong clusters; petals 5, scarcely ]/§ inch long, white; 



fruits tiny pods PETROPHYTUM, p. 135. 



Flowers large, usually borne singly; petals mostly 8, about 1/3 to Yi inch long, 



white or yellow; fruits small seed-like achenes with long white-fuzzy tails 



dryas, p. 136. 



B. Plants erect or spreading, or if low and creeping, not alpine dwarfs. 



1. Leaves compound (divided into separate leaflets). 

 Stems not thorny nor prickly. 



Leaves finely divided and fern-like. 



Low shrub not over 2 feet high; leaves three times divided; herbage with 



strong aromatic odor CHAMAEBATIA, p. 100. 



Erect shrubs 2 to 6 feet high ; leaves twice divided ; herbage with sweetish 



odor when crushed CHAMAEBATIARIA, p. 100. 



Leaves not fern-like. 



Leaves oblong to elliptic, 2'/2 to 8 inches long, usually with more than 5 

 leaflets; flowers white, borne m compact clusters; fruits apple-like 

 SORBUS, p. 109. 



Leaves roundish, not more than 1 inch long, divided into 3 to 5 leaflets; 

 flowers borne singly or in few-flowered clusters. 



Erect or spreading shrubs; leaflets grayish-green, not toothed; flowers 



yellow; fruits tiny seed-like achenes POTENTILLA, p. 101. 



Shrubs with trailing stems; leaflets dark green, irregularly toothed; 

 flowers white; fruits aggregate berries composed of several 



1 -seeded drupelets RUBUS, p. lOL 



Stems thorny or prickly. 



Leaflets mostly egg-shaped, roughish, prominently veined; flowers white or dark 

 red; fruits aggregate berries with many 1 -seeded drupelets 



RUBUS, p. 101. 



Leaflets mostly elliptic to oblong, smooth, not rough, obscurely veined; flowers 



rose-pink; fruits apple-like ROSA, p. 111. 



2. Leaves simple (not divided into separate leaflets). 

 Stems with stout thorns; flowers white, borne in flattish clusters at the ends of the 



stems; fruits dark purple or red, apple-like CRATAEGUS, p. 118. 



Stems not thorny (the ends of the branchlets sometimes spine-tipped in one species of 

 Prunus) ; flowers white, pink, or yellow, borne singly or in clusters; fruits 

 Various. 



Leaves not leathery, never linear nor divided into linear lobes. 



Flowers flat-spreading or saucer-shaped, the sepals persistent; petals present. 



Flowers borne singly or in few- to many-flowered clusters, the petals 

 mostly J/^ to 1 inch long; fruits fleshy. 



