Contraction of the Roots and Crowns Medicago and Melilotus

The longitudinal contraction, a natural phenomenon of many plants, which results in lowering the basal portion of the plant deeper in the soil, is apparently accomplished in various ways. In both alfalfa and sweet clover the crowns are pulled vertically downward two to four inches during the first season. This is accomplished chiefly by the contraction vertically and the expansion radially and tangentially of parenchymatous cells that are continuously being formed in isolated groups scattered among the vascular elements. The development and expansion of these intercalated masses of parenchyma separate the vascular elements into tortuous strands, the tortuosity of which results in the shortening of the entire vascular cylinder. The strands of libriform fibers in the cortex are shortened in the same manner

The Libriform Fibers in the Roots and Crown of Medicago and Melilotus

The libriform fibers, long known to be especially prominent in many of the Leguminsoae, particularly the papilionaceae, constitute a large part of the xylem and are present in the phloem of the roots and crowns of the alfalfas and sweet clovers. They deserve mentioning in these legumes because the modifications they undergo at different periods in the plant\u27s growth cycle indicate that they function as storage structures, and have an importance relative to the nutrition of the plant