FLOWERING PLANTS AND FERNS OF ARIZONA 441 



Black medick, nonesuch. A troublesome weed in lawns in some 

 parts of the United States. Although usually annual, this plant 

 shows a tendency to perennial growth in Arizona. 



3. Medicago hispida Gaertn., Fruct. et Sem. 2: 349. 1791. 

 Maricopa, Pinal, Cochise, and Pima Counties, occasional in waste 



land, March to April. 



Bur-clover. Extensively naturalized in California and elsewhere 

 in the United States. 



4. Medicago apiculata Willd., Sp. PL 3: 1414. 1805. 

 Eloy (Pinal County), at roadside. 



Often regarded as merely a variety of M . hispida. 



19. MELILOTUS. Sweetclover 



Plants annual or biennial, with leafy branched stems; herbage 

 fragrant when dried; leaves trifoliolate, the leaflets dentate; flowers 

 small, in elongate narrow racemes; calyx nearly regular; petals white 

 or yellow; stamens diadelphous, the anthers all alike; pods small, 

 ovoid or globose; seeds 1 or few. 



Coumarin, the substance that gives the strong odor to these plants, 

 makes them distasteful to livestock at first, but animals acquire a 

 liking for them, especially for the cured hay; and white sweetclover 

 {M. alba) is now cultivated as a forage plant in some parts of the 

 United States. Sourclover (M. indica) is extensively grown in the 

 Southwest as a winter cover crop and occasionally escapes from culti- 

 vation. These plants, especially M. alba, do well on moderately 

 saline soil. They are excellent honey plants. The Arizona species 

 are all introductions from Eurasia. 



Key to the species 



1. Flowers not more than 2.5 mm. long; stems commonly less than 1 m. long; 



corolla yellow ; pods alveolate-rugose 1. M. indica. 



1. Flowers not less than 4 mm. long; stems often more than 1 m. long (2). 



2. Corolla yellow, the banner not or but slightly surpassing the wings ; pods rugose. 



2. M. OFFICINALIS. 



2. Corolla white, the banner considerably surpassing the wings; pods not rugose, 

 inconspicuously reticulate 3. M. alba. 



1. Melilotus indica (L.) AIL, Fl. Pedem. 1: 308. 1785. 



Trijolium melilotus indica L., Sp. PI. 765. 1753. 



Coconino County (Havasu Canyon), Maricopa, Pinal, and Pima 

 Counties, occasional at roadsides, along ditches, and in fields, April to 

 September. Sourclover. 



2. Melilotus officinalis (L.) Lam., Fl. Franc, 2: 594. 1778. 



Trijolium melilotus officinalis L., Sp. PL 765. 1753. 



Coconino County, near Flagstaff and Williams, about 7,000 feet, 

 Pinal Mountains (Gila County), July to October. Yellow sweetclover. 



3. Melilotus alba Desr. in Lam., Encycl. 4: 63. 1797. 



Lees Ferry and Havasu Canyon (Coconino County), Chiricahua 

 Mountains (Cochise County), Sacaton (Pinal County), nowhere 

 abundant in Arizona. White sweetclover. 



