Ribes plant stem. Light micrograph (LM) of a cross-section through the woody stem of a ribes plant. Ribes is a genus of about 200 known species of flowering plants. The various species are known as currants or gooseberries, and some are cultivated for their edible fruit or as ornamental plants. The outer cortex (brown) is made of cork cambium tissue, beneath which is a ring of phloem and sieve tube bundles. Under this is a ring of cambium and then woody fibres. The solid pith (centre), is composed of large parenchyma cells. Magnification: x10 when printed 10 centimetres wide.