The development of the tuber in seedlings of five species of Dioscorea from Nigeria

Tubers in all five species develop from the hypocotyl region of the seedlingS. A perivascular cambium arises cutting off mainly starch-storing parenchyma and collateral vascular bundles to the inside. A phellogen gives rise to cork on the outside. Between the two cambial layers there may or may not be layers of parenchyma, not storing starch but containing raphides. The vascular bundles consist of xylem with vessels, scalariform tracheids and parenchyma; and phloem, with sieve tubes and parenchyma.