114 FODDER AND PASTURE PLANTS. 



ALFALFA (Medicago sativa L.) 



Plate 21 ; Seed, Plate 27, Fig. 34. 



Other English name: Lucerne. 



Botanical description: Alfalfa is a strongly perennial plant 

 which is able to live thirty years or more under favourable conditions. 

 It has a typical taproot; that is, the root system consists of a strong 

 main root from which secondary side roots branch off. As there are 

 no runners or creeping roots, all the overground branches start from 

 the uppermost part of the taproot which generally protrudes above 

 the ground and is known as the crown. With increasing age, the 

 crown is apt to split into two or more branches, the upper ends of 

 which are free and form a kind of tuft, sometimes of considerable 

 circumference. The main root, which when old is an inch or so 

 thick and rather woody, finds its way down to a considerable depth 

 if the soil permits. On the roots are found the nodules, typical of 

 the leguminous plants. They are on the finer branches and are 

 clustered together into irregular bunches. The stems, which in old 

 plants are exceedingly numerous, are generally from two to three feet 

 high at flowering time. As a rule, they are little branched, especially 

 when the stand is dense. They are round below, more or less angular 

 towards the top, and usually smooth. The leaves, which are alter- 

 nate (that is, solitary at each joint and scattered along the stem), 

 consist of three leaflets like those of Red Clover. The leaflets are 

 rather narrow, two to three times as long as broad, and sharply 

 toothed in their upper part. The middle one has a short stalk 

 whereas in the cultivated species of Trifolium the central leaflet has 

 no stalk. Occasionally leaves with four or five leaflets are found 

 but not so often as in Red Clover. 



Biology of flower: The flowers are in a short and somewhat 

 one-sided cluster. Each cluster contains from ten to twenty purple 

 flowers of the ordinary leguminous shape, as described on page 15. 

 They are fertilized by means of insects, especially certain kinds of 

 bees. In all leguminous plants fertilized in this way, the stamens 

 may come into close contact with the body of the insect. A bumble 

 bee, for instance, visits Alfalfa. The nectar being in the bottom of 

 the flower, it has to poke its proboscis down to the bottom of the 

 flower tube. When it comes in contact with the lower part of the 

 blossom, it works like a touch on the trigger of a gun. The cluster 

 of stamens is set like a spring, and the touch throws the upper part 

 of stamens and pistil forward with a jerk. An insect sitting on the 



