220 MAPLE ORDER 



b. Wings of fruit narrow ; flower cluster nearly 



sessile A. grandidentdtum 



ANACARDIACEAE SUMAC FAMILY 



Sepals 4-6, united, petals 4-6, rarely none, stamens 5, ovary usually 1- 

 celled, styles 3, fruit usually a drupe; flowers polygamous, in axillary or 

 terminal panicles ; trees or shrubs with alternate, 3-foliate, odd-pinnate 

 leaves. 



Rhus Linne 1753 Sumac, Poison Ivy 



(Gr. rhons, sumac, perhaps from the Celtic for red) 



PL 34, fig. 3-5. 



Characters of the family. 



1. Leaflets 3 



a. Leaflets 1-4 in. long, broadly ovate, toothed; 



stems little branched, 3 in. -2 ft. high ; poison- 

 ous to the touch R. Rydbergii 



b. Leaflets .5-1 in. long, wedge-shaped to obo- 



vate, usually lobed ; stems bushy, 1-8 ft. high R. trilobdta 



2. Leaflets 11-31, lanceolate, 2-6 in. long; stems 3- 



12 ft. high R. glabra 



BETULACEAE BIRCH FAMILY 



Sepals 2-4, united, or none, petals 0, stamens 2-10, ovary 1-2-celled, 

 fruit a 1-seeded nut, sometimes with an involucre; flowers monoecious in 

 catkins ; trees or shrubs with alternate, simple often lobed, toothed leaves. 



1. Fruits in spikes or catkins 



a. Bracts of the fruiting catkin papery, 3-lobed, 



falling with the small nut Betula 



b. Bracts of the fruiting catkin thick, not 3-lobed, 



persistent Alnus 



2. Fruit a large nut in a tubular involucre, paired Corylus 



Alnus Linne 1753 Alder 



(Lat. alnus, alder) 



PI. 34, fig. 8. 



Sepals of the stamen flower 3-5, united, of the pistil flower none, petals 

 0. stamens 2-5, stamen catkins with 4-5 bractlets and 3 or 6 flowers upon 

 each stalked, shield-shaped scale, pistil catkins with 2 flowers in the axil of 



