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114   FODDER AND PASTURE PLANTS.

ALFALFA (*tedicago saliva 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 alternate (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


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