442 BOTANY or CROP PLANTS 



ovary is sessile or short-stipitate, and several- or rarely one- 

 ovuled; it has a subulate (awl-shaped), and smooth style. 

 The pods (Fig. 187) are curved or spirally twisted, veiny or 

 spiny, and indehiscent. 



Geographical. — There are a number of species of Medi- 

 cago, all of which are native to the eastern hemisphere. They 

 naturally range from Eastern Asia to Southern Africa. 

 There are seven perennial species of Medicago, and about 37^ 

 annual species, one of which, yellow trefoil (Medicago lupu- 

 lina), has a biennial or possibly perennial form: The non- 

 perennial species are commonly known as "bur clovers." 

 They will grow naturally as winter annuals. 



Key to Peincipal Species of Medicago 



Perennial, erect-growing plants; flowers violet, Medicago saliva (alfalfa). 

 Annual, low-growing plants; flowers yellow. 



Pods kidney-shaped, without spines, Medicago lupulina (hop clover). 

 Pods cylindrical, with spines. 



Stems pubescent; pods 33^^ to 5 millimeters diameter; purple spot in 

 center of each leaflet; two to eight seeds in each pod, Medicago arabica 

 (spotted bur clover). 

 Stems glabrous, pods 7 to 10 millimeters diameter; no purple spot in 

 center of each leaflet; three to five seeds in each pod, Medicago 

 hispida (toothed bur clover). 



MEDICAGO SATIVA (Alfalfa, Lucerne) 



Roots. — Alfalfa is a deep feeder. The young plant usually 

 sends down a single tap root. As a rule, this takes a straight 

 downward course. Comparatively few side roots are given 

 off. Usually, these are below the depth of 4 feet. Headden 

 found in a plant only nine months old, that the young roots 

 had extended to a depth of over 9 feet. Ordinarily the weight 

 of roots exceeds weight of top. 



Stems. — Alfalfa is an ascending or erect perennial. Its 

 life period is dependent upon environmental conditions and 



