KEY TO THE SPECIES 47 



1. Euphorbia marginata Purah ("Snow-on-the-mountain "). Stout, erect, 

 hairy, 3-6 dm. high ; leaves ovate, oblong or obovate ; the floral leaves (bracts) 

 large, white-margined (petal-like) ; inflorescence umbel-like ; involucres bell-shaped, 

 5-lobed, the alternating glands with white reniform appendages ; capsule sub- 

 globose. Frequent on sandy plains. 



2. Euphorbia robusta (Engelm.) Small (Rocky Mountain Spurge). Smooth 

 and glaucous, the numerous erect stems tufted ; leaves ovate to oblong, 1-3 cm. 

 long ; inflorescence an umbel ; involucres campanulate, the glands naked ; pod 

 globose, nodding ; the seeds with shallow pits. Frequent on stony, sandy ridges and 

 slopes. 



3. Euphorbia petaloldea Engelm. (White-flowered Spuroe). Low, 

 slender branched, spreading or prostrate ; leaves opposite, mostly oblong, 1-2 cm. 

 long, entire ; involucre bell-shaped, 4-lobed ; glands with conspicuous white 

 petaloid appendages ; the ash-colored seeds nearly smooth. Very abundant on 

 warm sandy slopes. 



XXXVI. OXALIDACEiE (Sokrel Family) 



Herbs with alternate or basal 3-foIiolate leaves, regular 

 flowers, 5 sepals, 5 petals, 10 stamens usually united at base, 5 

 styles and a 5-celled ovary becoming a 5-lobed pod. 



1. OXALIS (WOOD-SOKKEL) 



Herbs with sour juice, and inversely heart-shaped leaflets (closing and drooping 

 at night). 



1. Oxalis stricta L. (Yellow Wood-sorrel). Smooth or hairy, from running 

 rootstocks ; stems leafy, branching, bearing axillary flower-stalks longer than the 

 leaves and with 2-6 yellow flowerg. 



XXXVII. ACERACEiE (Maple Family) 



Trees with opposite simple or compound leaves, small regu- 

 lar flowers, usually a 5-lobed colored calyx, petals often none, 

 3-12 stamens, 3 long styles, and a 2-lobed ovary ripening into a 

 pair of winged fruits. 



1. ACER (Maple) 



Trees with palmately lobed leaves. (See Plant Relations, p. 26, Fig. 20 ; also 

 p. 115, Fig. 116. Also Plant Structures, p. 212, Fig. 186.) 



1. Acer saccharinum L. (White or Silver Maple). Ornamental tree ; 

 leaves very deeply 5-lobed, with rather acute sinuses, silvery-white underneath, 

 the divisions narrow, cut-lobed and toothed ; flowers in lateral umbel-like clusters 

 on short stalks, much preceding the leaves ; stamens 3-6 ; fruit with large divergent 

 wings. Freely planted in parks and home grounds. 



2. Acer glabrum Torr. (Rocky Mountain Maple). Generally a shrub in 

 small clumps, or singly and tree-like ; leaves 3-lobed or 3-parted, the segments 



