STUDIES ON THE COTYLEDONARY LEAVES OF SOME CONVOLVULACEAE

SummaryThe usefulness of the cotyledonary leaf characteristics in the taxonomy of Convolvulaceae has been highlighted. Certain characters of the mature cotyledonary leaves of seedlings, such as the mean area, depth of lobing, depth of basal sinus, angle between the lobes, pattern of venation, stalk length and other features offer much scope for the taxonomists, in view of their high level of constancy. Furthermore, being quite conservative, these characters shed considerable light on the systematic relationship existing among the taxa. The cotyledonary leaves of Merremia tridentata are very similar to those of Ipomoea coptica, suggesting parallel evolution. Among the varieties of I. nil and I. batatas, there exist certain differences, while the two varieties of I. pes‐tigridis register greater similarity. Evolvulus alsinoides and E. nummularius show but a slight difference in size. Cressa cretica is unique in having linear cotyledons. Cuscuta chinensis stands apart from the rest of the family, being acotyledonous, thus affording yet another reason for its segregation from Convolvulaceae. Rivea hypocrateriformis and Argyreia cuneata show similar characteristics, giving additional support in favour of the generic merger of Rivea with Argyreia.