MORACEAE (MULBERRY FAMILY) 143 



spinulose: cup hemispheric, 7-10 mm. broad; scales ovate, strongly corky- 

 thickened on the back; acorn barrel-shaped or cylindric, 10-15 mm. long, 

 6-7 mm. in diameter, brown (Q. pungens Liebm., Rydb. 1. c.). Colorado to 

 Texas and Arizona. 



31. ULMACEAE Mirbel. ELM FAMILY 



Trees or shrubs with alternate serrate pinnately veined leaves, with fugaci- 

 ous stipules. Flowers small, monoecious, dioecious, or polygamous, clustered 

 or the pistillate solitary. Perianth of 4-9 distinct sepals. Stamens as many 

 as the sepals. Ovary 1-celled, superior. Fruit a samara, drupe, or nut. 



All the flowers clustered; fruit a samara 1. Ulmus. 



Pistillate flowers solitary; fruit a drupe 2. Celtis. 



1. ULMUS L. ELM 



Trees with polygamous purplish or yellowish flowers in lateral clusters, ap- 

 pearing before the short-petioled oblique or unequally somewhat heart-shaped 

 leaves. Perianth campanulate. Stamens slender, 4-9. Styles 2, diverging, 

 stigmatic along the inner margin. Fruit 1-seeded, winged all around. 



1. Ulmus americana L. Sp. PI. 226. 1753. Large and well-known orna- 

 mental tree, usually with spreading branches and drooping branchlets: buds 

 and branchlets glabrous: branches not corky: leaves obovate-oblong or oval, 

 abruptly pointed, sharply and often doubly serrate (5-10 cm. long), soft- 

 pubescent beneath, or soon glabrous: flowers in close fascicles: calyx with 7-9 

 roundish lobes: fruit glabrous except the margins (12 mm. long), its sharp 

 points incurved and closing the notch. Probably not indigenous in our range, 

 but largely grown as a shade tree. 



2. CELTIS L. HACKBERRY 



Leaves pointed, petioled. Flowers greenish, axillary, the fertile solitary or in 

 pairs, peduncled, appearing with the leaves; the lower usually staminate only, 

 in little fascicles or racemose along the base of the branches of the season. 

 Calyx 5-6-parted. Stamens 5-6. Ovary 1-celled. Fruit globular. 



1. Celtis occidentalis L. Sp. PI. 1044. 1753. Leaves reticulated, ovate, 

 Cordate-ovate and ovate-lanceolate, taper-pointed, sharply serrate, some- 

 times sparingly so or only towards the apex, scabrous but mostly glabrous 

 above, usually soft-pubescent beneath, at least when young: fruit reddish or 

 yellowish, becoming dark purple. From Colorado to Wisconsin and east- 

 ward. A small or middle-sized tree with the aspect of an elm. 



32. MORACEAE Lindl. MULBERRY FAMILY 



Trees, shrubs, or herbs with opposite lobed leaves (our only native genus an 

 herbaceous vine). Flowers dioecious. Calyx 5-parted. Petals none. Sta- 

 mens 5. Ovary superior, 1-celled, 1-ovuled, becoming a glandular or resinifer- 

 ous achene. Ulmaceae in part. 



1. HUMULUS L. HOP 



Twining rough perennials, with stems almost prickly downwards, and mostly 

 opposite, heart-shaped, and palmately 3-7-lobed leaves. Sterile flowers with 

 5 sepals and 5 erect stamens. Fertile flowers in short spikes with leafy im- 



