Leaf Architecture of Some Monocotyledons with Reticulate Venation

Twelve species belonging to seven monocotyledonous families: Hydrocharitaceae, Taccaceae, Dioscoreaceae, Smilacaceae, Araceae, Alismataceae and Aponogetonaceae show reticulate venation typical of dicotyledons. A study of the leaves of these species shows that venation patterns are usually curvipalmate-convergate, occasionally rectipalmate or collimate, and rarely pinnate lyrate type. Number, size and shape of areoles, number of primaries, number of secondaries along one side of the primaries, angle between 1 and 2° veins and number of vein endings per areole are given for each species. Intesecondary veins, isolated tracheids, loops, extension cells, raphide and raphide idioblasts and terminal tracheids were observed. Marginal ultimate venation is mostly arcuate. Major and minor veins are jacketed by parenchymatous bundle sheath cells. The lamina of Tacca leontopetaloides, Colocasia esculenta and Scindapsus aureus show a single midrib-like central region similar to that of dicotyledonous leaves, and it is multistranded in Aponogeton natans, Limnophyton obtusifolium and Ottelia alismoides. The degree of vein order is most commonly up to fourth or fifth and rarely up to sixth in Dioscorea hispida.