304 THE KINDS OF PLANTS 



5. CANNABIS. Hemp. 



Tall, strong, dioecious herbs with 5 to 7 leaflets: fertile flowers in clus- 

 ters, with 1 sepal surrounding the ovary, and 2 long, hairy stigmas: sterile 

 flowers in racemes or panicles, with 5 sepals and 5 drooping stamens. 



C. sativa, Linn. Hemp. Six to 10 ft., strong-smelling, blooming all 

 summer: leaflets lanceolate, large toothed. Old World; cultivated for fiber 

 and sometimes escaped in waste places. 



6. HtMULUS. Hop. 



Twining dioecious herbs of tall growth, with 5 sepals in the sterile 

 flowers, the stamens erect: fertile flowers with 1 sepal, 2 flowers under each 

 scale of a short, thin catkin which becomes a kind of cone or " hop." 



H. Lupulus, Linn. Common hop. Perennial, rough-hairy: leaves broad - 

 ovate, deeply 3-lobed (only rarely 5-7-lobed): sterile flowers in panicles 

 2-6 in. long: pistillate catkin enlarging into a "hop" often 2 in. or more 

 long. A native plant, cultivated for hops and sometimes for ornament. 



H. Jap6nicus, Sieb. & Zucc. Japanese hop. Fig. 107. Annual: leaves 

 not less than 5-lobed: fertile catkin not enlarging into a hop. Japan; much 

 cultivated for ornament. 



7. tTRTICA. Nettle. 



Erect herbs with opposite simple leaves and stinging hairs, and mon- 

 oecious or dioecious flowers in racemes or dense clusters, the calyx of 4 

 separate sepals: stamens 4: stigma sessile: fruit an ovate flat akene. The 

 following are perennials with flowers in panicled spikes. 



U. gracilis, Ait. Common nettle. Two to 6 ft. : leaves ovate-lanceolate, 

 serrate, on long petioles. Common in low grounds. 



U. rtioica, Linn. Not so tall: leaves ovate-cordate and deeply serrate, on 

 rather short petioles, downy underneath. Weed from Europe, very stinging. 



IX. POLYGONACE^. Buckwheat Family. 



Herbs, mostly with enlarged joints or nodes and sheaths (repre- 

 senting stipules) above them : leaves simple and usually entire, 

 alternate : flowers small, apetalous, usually perfect and generally 

 borne in spikes or dense clusters : stamens 4-12, attached to the 

 very base of the 3-5-merous calyx : ovary 1-loculed, ripening into a 

 3-4-angled akene. Thirty or more genera and about 600 widely dis- 

 persed species. Characteristic plants are buckwheat, rhubarb, dock, 

 sorrel, smartweed. 



A. Root-leaves 1 ft. or more across, rounded 1. Rheum 



aa. Root-leaves narrow or not prominent. 



b. Calyx of 6 sepals, often of two kinds 2. Bumex 



bb. Calyx of 5 (rarely 4) sepals, all alike. 



c. Flowers white and fragrant 3. Fagopyrnm 



CC. Flowers greenish or pinkish, not distinctly fragrant. 4. Polygonum 



