72 MOKACEAE 



Flowers preceding leaves ; fruit a samara. 1. Ulmus. 



Flowers with leaves ; fruit a drupe. 2. Cbltis. 



1. TJLMUS L. 



Trees with serrate, strongly-veined, obovate, inequilateral leaves. 

 Flowers perfect or polygamous, fascicled or racemose, on jointed pedicels. 

 Samara winged all around. 



Flowers fascicled. 



Samara eiliate. 1. U. Americana. 



Samara smooth. 3. U. pubescena. 



Flowers racemose. 2. U. racemosa. 



1. U. Americana L. White Elm. Often 120° high ; branches not 

 corky-winged : leaves smoothish above : flowers long-pedioelled. — Com- 

 mon along streams. March-April. 



2. U. racemosa Thonias. Cork Elm. Like the last : branches often 

 corky- winged : samaras densely eiliate. — In rocky woods along the Mis- 

 souri Eiver bluffs from Kansas City to Little Blue River. March-April. 



3. U. pubescens Walt. Slippery Elm. Sometimes 70° high: twigs 

 and bud-scales pubescent : leaves rcngh-pubesoent above : flowers short 

 pedieelled. — A common forest tree. March-April. 



2. CELTIS Tourn. Hackbkrry. 

 Trees with pinnately-veined leaves and axillary polygamous flowers. 

 Staminate flowers clustered. Fertile flowers one or two together and 

 peduncled. Calyx 5-6-parted. Fruit a globular drupe. 



Leaves serrate. 1. C. occidentalis. 



Leaves entire. 2. C. Mississippiensis. 



1. C. occidentalis L. A small or large tree with ovate or ovate-Ianoe- 

 olate, sharply serrate, inequilateral leaves : drupe 4"-5''' diameter. — 

 Common along streams and bluffs. April-May. 



2. C. Mississippiensis Bosc. A small tree with lanceolate- ovate, en- 

 tire or nearly so, leaves : drupe 2^-3'^ in diameter. — In bottoms along 

 the Missouri Eiver near Courtney and Sibley and on rooky hills near 

 Westport and Independence. Local. April-May. 



Var. pumila (Pursh) Mackenzie & Bush, n. comb. 3° -8° high : leaves 

 less taper pointed and drupe larger. — Eocky banks north of Lee's Summit. 

 { C. pumila Pursh. ) 



Family 33. MORACEAE Lindl. 

 Flowers monoecious or dioecious, small, axillary and clustered. Calyx 

 4-5-parted, the stamens as many as its lobes. Ovary 1-celled, superior, 

 1-ovuled. 



Trees or shrubs. 



Leaves serrate. ] . MoRUS. 



Leaves entire. 2. TOXYLON. 



A twining vine. 3. HuMULUS. 



An erect herb. 4. Cannabis. 



