Venation

Venation is the arrangement of veins and veinlets on the lamina, which internally carry the vascular tissue. It is broadly of two kinds. Reticulate venation, in which the veins branch and rejoin (anastomose) into a network, is characteristic of dicot leaves and is of two types: pinnately reticulate (unicostate), with a single central midrib giving off many branching lateral veins (Mangifera indica, Ficus religiosa, Nerium), and palmately reticulate (multicostate), with two or more principal veins arising from one point - either diverging toward the margin (Cucurbita, Luffa, Carica papaya) or converging again toward the apex (Zizyphus, Cinnamomum). Parallel venation, in which the veins run alongside each other without forming a prominent network, is characteristic of monocot leaves and is likewise of two types: pinnately parallel (unicostate), with one central midrib giving off many veins that run parallel to each other (Musa, Zingiber, Curcuma, Canna), and palmately parallel (multicostate), with several veins arising together from the petiole tip and running parallel - diverging toward the margin as in the fan palm Borassus flabelliformis, or converging again at the apex as in bamboo, rice and water hyacinth. …