TAXONOMIC SIGNIFICANCE OF VESSEL ELEMENTS IN THE TILIACEAE

Internodal vessel elements were investigated in 7 genera and 27 specie s of the Tiliaceae with special reference to their taxonomic significa nce. On average, the longest Vessel elements are 441 mu m, recorded in Grewia asiatica and Triumfetta rhomboidea, and the shortest 78 mu m, in Grewia microcos. The average maximum diameter is 79 mu m in Corchor us aestuans, and the minimum 22 mu m in Grewia microcos. The vessel el ements are either cylindrical, spindle-shaped, column-, drum- or funne l-like, conical, clavate or oval. Perforation plates are simple in all the species studied, except in Grewia asiatica, where ephedroid-like perforation plates were recorded. There are usually two perforation pl ates in the majority of the members, rarely three or one. Adjacent wai l thickening is commonly simple-pitted, but bordered, reticulate or sc alariform pits have also been observed. Vessel elements vary in form a nd structure, number and inclination of perforation plates and side wa ll thickening. These characters are of taxonomic importance.