URTICACEAE. 101 



Fruit an achene, the achenes sometimes in tlie accrescent sepals and forming a 

 syncarp. 

 Flowers not on a receptacle : fruit not syncarps : 

 sepals neither thick and juicy nor enveloping 

 achenes. 

 Style or stigma 1 : the latter sometimes tufted : 



ovule erect : filaments inflexed in the bud. Fam. 1. Urticaceae. 



Styles or stigmas 2 : ovule pendulous : filaments 



erect in the bud. Fam. 2. Caxnabinaceae. 



Flowers on the outside or inside of a receptacle : 

 fruits syncarps or syconiums : sepals accrescent, en- 

 veloping the achenes. Fam. 3. Artocarpaceae. 

 Fruit a samara or a drupe, sometimes nut-like. Fam. 4. Ulmaceae. 



Family 1. URTICACEAE. Nettle Family. 



Herbs or shrubby plants, often with stinging hairs. Leaf-blades entire, 

 toothed, or rarely lobed. Flowers dioecious, monoecious, or polygamous, 

 cymose. Calyx of 2-5 distinct or partially united sepals. Androecium of 

 2-5 stamens. Gynoeeinm a single carpel. Fruit an achene. 



Sepals of the pistillate flowers distinct or slightly united, not investing the achene. 



Stigma subulate, not tufted : ovary, and achene. oblique. 1. Urticastruji. 

 Stigma tufted : ovary, and achene, equilateral. 

 Flowers not involucrate. 



Pistillate flowers with 4 sepals : staminodia wanting. 2. Urtica. 



Pistillate flowers with 3 sepals : staminodia present. 3. Adicea. 



Flowers involucrate. 4. Parietaria. 

 Sepals of the pistillate flowers united, the tube wholly investing 



the achene. 5. Boeiimeria. 



1. URTICASTRUM Fabr. Perennial herbs with stinging hairs. Leaves 

 alternate: blades toothed. Pistillate flowers with a calyx of 5 sepals and an 

 oblique ovary. 



1. U. divaricatum (L.) Kuntze. Stem 2-12 cm. tall: leaf -blades ovate, oblong, 

 or elliptic, 5-20 cm. long, long-petioled: panicles spreading, the lower stami- 

 nate, the upper pistillate: sepals oblong, or broader in the pistillate flowers: 

 achene oblique, about 3 mm. in diameter, exserted. — Common, in thickets 

 and in woods. — fSum. — Wood-nettle. 



2. URTICA [Tourn.] L. Annual or perennial often coarse herbs with 

 stinging hairs. Leaves opposite: blades toothed or inciseddobed. Pistillate 

 flowers with a calyx of 4 sepals and an equilateral ovary. — Sum. — Nettle. 



Stems sparingly bristly : petioles fully % as long as the width of the leaf-blades. 



1. U. gracilis. 

 Stems densely bristly : petioles less than i/o as long as the width of 



the leaf-blades. 2. V. dioica. 



1. U. gracilis Ait. Stem 6-28 dm. tall: leaf -blades lanceolate, occasionally 

 broadly so, 6-15 cm. long, acuminate, serrate: sepals hispidulous: achenes 

 fully 1 mm. long. — Rather rare, in fence-rows and on river banks. 



2. U. dioica L. Stem 6-13 dm. tall: leaf-blades ovate to ovate-lanceolate, 

 3-12 em. long, prominently incised-serrate, cordate, sometimes deeply so: 

 sepals sof t-hispidulous : achenes fully 1 mm. long. — Eather common, in waste 

 places and on roadsides. Nat. of Eu. — Sttnging-nettle. 



3. ADICEA Eaf. Annual or perennial erect succulent herbs. Leaves 

 mainly opposite: blades toothed, 3-ribbed. Flowers dioecious. Sepals of the 

 pistillate flowers 3, equal, slightly broader at the apex, not enclosing the achene, 

 each accompanied by a staminodium. Stigma tufted. 



1. A. pumila (L.) Eaf. Stem 1-7 dm. tall, very watery: leaf -blades ovate to 

 elliptic, 3-10 cm. long, coarsely crenate-serrate, long-petioled: sepals lanceo- 



