FLOWERING PLANTS AND FERNS OF ARIZONA 255 



3. Leaf blades usually narrower, lanceolate or linear-lanceolate Co). 



5. Inner sepals without callosities 4. R. califorxicus. 



5. Inner sepals all, or 1 of them, bearing a callosity, this much narrower 

 than the sepal (6). 

 6. Inner sepals about 4 mm. long; achenes about 2.5 mm. long. 



5. R. mexicaxus. 

 6. Inner sepals about 3 mm. long; achenes about 2 mm. long. 



6. R. TRIAXGULIVALVIS. 



2. Stems usually erect and without axillary shoots (7). 



7. Callosities wanting on the inner sepals but the midnerve sometimes 

 thickened (8). 

 8. Inner sepals in fruit 10 mm. long or longer, deeply cordate, usually 

 reddish; stipular sheaths firm, persistent; leaf blades thickish. 



7. R. HYMEXOSEPALUS. 



8. Inner sepals in fruit 4 to 5 mm. long; sheaths delicate, fugacious; 

 leaf blades thinnish, the basal ones very large (9). 

 9. Lower leaves rounded or cuneate at base, the lateral veins divaricate. 



forming a right angle with the midvein 8. R. orthoxeurus. 



9. Lower leaves more or less cordate at base, the lateral veins somewhat 

 ascending, forming a smaller angle with the midvein. 



9. R. occidextalis. 

 7. Callosities present on at least 1 of the inner sepals (10). 



10. Inner sepals entire or, if denticulate, then the leaf margins usually 

 distinctly crisped (11). 

 11. Leaf blades small, flat, truncate or the lowest cordate at base; inner 

 sepals 2.5 to 3 mm. long, scarcely broader than the thick callosity; 

 inflorescence conspicuously leafy, much interrupted. 



10. R. CONGLOMERATES. 



11. Leaf blades large, crisped or undulate on the margin, commonly 



narrowed (seldom truncate) at base; inner sepals 4 to 6 mm. 

 long, much broader than the callosity; inflorescence not leafy and 



interrupted, or so only toward the base 11. R. chispus. 



10. Inner sepals dentate or denticulate (12). 



12. Plant perennial; basal leaves not more than 2.5 times as long as 



wide, cordate at base; inner sepals usually sharply and conspic- 

 uously dentate 12. R. OBTUSIFOLITS. 



12. Plants mostly annual; basal leaves 3 to 6 times as long as wide (13). 



13. Inner sepals 2.5 to 3 mm. long, short-dentate or denticulate; leaf 

 blades oblanceolate or obovate, commonly about 3 times as 

 long as wide i3. R. violascexs. 



13. Inner sepals not more than 2 mm. long, mostly long-dentate: leaf 

 blades linear-lanceolate, usually more than 3 times as long as 

 wide 14. R. fuegintjs. 



1. Rumex acetosella L., Sp. PL 338. 1753. 



Navajo, Graham, Gila, and Pima Counties, 5,500 to 8,000 feet, 

 occasional. Naturalized almost throughout temperate North America ; 

 native of Eurasia. 



Sheep sorrel. An abundant and troublesome weed of fields and 

 pastures in other parts of the United States. The herbage is very 

 sour to the taste, containing much oxalic acid. 



2. Rumex altissimus Wood, Class Book, ed. 2, 477. 1847. 

 Coconino, Graham, Gila, Cochise, and Pima Counties, 3,000 to 



7.000 feet. Eastern and central United States to Arizona. 



3. Rumex ellipticus Greene, Pittonia 4: 234. 1900. 



Pinal Mountains, Gila County (Peebles et al. 4432), Tucson, Pima 

 County (Tourney 343a), probably more widely distributed in the State. 

 Texas to Arizona. 



Scarcely more than a variety of R. altissimus. 



286744°— 42- 



