DISCUSSION OF SUBGENERIC CLASSIFICATION
Any attempt to revise the subgeneric classification of ssp. Philodendron is frustrated by the lack of correlation of morphological characteristics throughout the subgenus. Engler (1899) separated the species of P. subg. Philodendron primarily on the basis of leaf shape, leaf blade venation and the nature of the pistil, placentation and number of ovules. Most sections, all moderately small ones, were separated on the basis of leaf morphology. These include: P. sect. Tritomophyllum, P. sect. Schizophyllum, and P. sect. Polytomium. Two sections, namely P. sect. Macrogynium, and P. sect. Camptogynium are based on the nature of the pistil. Following a cladistic analysis of a relatively small number of species, including some in P. subg. Philodendron, Mayo (1986) concluded that it should be divided into two to three sections instead of the existing nine sections in the family. While I agree that P. sect. Macrolonchium should be reduced, I think that a cladistic analysis making use of the leaves as well would still justify the existence of the remaining sections recognized by Krause with the possible exception of P. sect. Camptogynium which was not studied by Mayo.