140 CHAPTER IX 



the age of the plant. It is characterised by its exceedingly 

 deep and well-developed tap-root, which often penetrates to 

 considerable depth, fifty feet and more. The more or less 

 kidney-shaped seeds are borne in special racemes springing 

 from the axils of the leaves. In the ordinary varieties under 

 cultivation, purple is the characteristic colour of the flowers, 

 and root-stocks are almost entirely absent. 



The places of origin of the medicagos are Europe and 

 Asia. The genus Medicago contains a large number of species. 

 Among the annuals the only ones of any agricultural import- 

 ance, and then not in the Union, are the Burr Clovers, the 

 chief of which is M. lupulina (Black Medick or Yellow 

 Trefoil). Three species belonging to the perennials are of 

 great agricultural value, namely, the H. sativa, M. falcata, 

 and by hybridisation of these two, M. media. The plant M. 

 sativa var. gaetula may prove of economic value because of 

 its tendency to produce rhizomes. 



Medicago sativa. — Nearly all varieties in common culti- 

 vation belong to this species. It is purple-flowered, has a very 

 pronounced tap-root, and produces numerous upright stems. 

 The plant in general is less bushy than in M. falcata. In 

 M. falcata the seed is carried in spiral pods. 



Medicago falcata. — This species is yellow-flowered, with 

 sickle-shaped pods. It also has numerous stems, but the plant 

 is usually more decumbent and the stems are finer than those 

 of sativa or media. It shows a tendency to have its crown par- 

 tially buried, and a few plants have been found with rhizomes. 

 The rooting system is more branched, and the tap-root less 

 developed. It is found in the natural state in Siberia, and, 

 consequently will stand extraordinary low killing tempera- 

 tures, and is very drought resistant. It is not ordinarily high 

 yielding. 



Medicago media. — This species has variegated flowers with 

 spiral pods. In growth it resembles sativa, but is hardier and 

 more resistant to drought and cold — qualities it owes to its 

 falcata parent. Most varieties of supposedly the sativa type 

 will be found to have some media characteristics. In cold, 

 dry climates, varieties such as Grimms', Sand or Variegated, 

 which are distinctly media, thrive better than varieties of 

 sativa, such as Arabian or Peruvian. 



Medicago sativa var. gaetula. — This species was im- 

 ported from Tunis to the United States. It is peculiar in 

 having abundant rhizomes up to 3| feet in length. The hybrid 



