to sections, subsections and series of P. subg. Philodendron
Pistils usually 2-locular, rarely 3-locular; eastern South America and
P. sect. Philopsammos
1b. Pistils 4-10-locular; throughout the range of the genus.
straight, directed in the same axis as the ovary; Central and South America.
P. sect. Macrogynium
Blades pinnately or bipinnately lobed; the divisions more or less uniform
along the anterior lobe; Central and South American species.
P. sect. Polytomium
10b. Petioles terete or subterete.
15a. Cataphylls decidduous intact or sometimes becoming fibrous but soon deciduous
P. ser. Philodendron Schott
P. giganteum (not in Central America)
15b. Cataphylls persisting as a mass of fibers
16a. Blades matte on lower surface.
17a. Blades matte, not velvety on upper surface, whitish and glaucous on lower surface P. ser. Impolita Croat [P. hebetatum, P. strictum., P. thalassicum]
17b. Blades velvety on upper surface, not whitish and glaucous on lower surface P. ser. Velutina Croat [P. gigas]
16b. Blades usually semiglossy, never whitish or glaucous, on lower surface.
18a. Sap brown to clear, never P. ser. Fibrosa, Croat [P. alticola, P. antonioanum, P. breedlovei, P. chiriquense, P. dodsonii, P. grandipes, P. jodavisianum, P. lazorii, P. llanoense, P. panamense, P. pirrense, P. purulhense, P. scalarinerve, P. schottianum. P. tenue.]
18b. Sap white and chalky
P. ser. Albisuccosa Croat [P. albisuccus]
9b. Blades acute to obtuse at base; petioles subterete and smooth8b. Pistils with basal or sub-basal placentation; ovules few per locule, usually fewer than 5, seldom up to 8, rarely as many as 12 (but with some locules in the same inflorescence with us few as 6 ovules per locule)
P. subsect. Canniphyllum (Schott) Mayo [P. chirripoense, P. cretosum, P. roseospathum]
19a. Plants usually appressed hemiepiphytic climbers; internodes frequently as long as wide or longer than wide; widespread in both Central and South America.19b. Plant habit unknown; internodes much broader than long; Colombia (exact locality unknown) P. subsect. Eucardium (Engl.) Mayo
20a. Blades deeply 3-lobed; cataphylls persisting in a dense, reddish brown layer of fibers; South American species only; P. acuminatissimum Engl. P bulaoanum Engl P. subsect. Bulaoana Mayo
20b. Blades not at all 3-lobed, cordate, sagittate, or ± oblong; cataphylls deciduous or persistent, fibrous or intact; widespread in both Central and South America.
21a. Inflorescences both small and numerous, usually more than 6 per axil, less than 5 cm long
P. subsect. Oligocarpidium (Engl.) Mayo [P. clewellii, P. heleniae]
21b. Inflorescences of normal size, typically I few and more than 5 cm long.
22a. Pistils with several ovules per locule; petioles rarely with purple ring at apex; blades sagittate or cordate at base P. subsect. Macrobelium
23a. Cataphylls deciduous.
24a. Leaf blades with minor veins not at all etched into upper surface P. ser. Macrobelium (Schott) Croat [P. advena, P. annulatum, P. aromaticum, P. coloradense, P. dwyeri, P. edenudatum, P. ferrugineum, P. grayumii, P. knappiae, P. mexicanum, P. platypetiolatum, P. sagittifolium, P. sousae, P. subincisum, P. verapazense, P. zhuanum]
24b. Leaf blades with minor veins etched into upper surface P. ser. Ecordata Croat [P. brenesii, P. crassispathum, P. davidsonii, P. lentii, P. niqueanum]
23b. Cataphylls persistent.
25a. Cataphylls weathering and persisting as fibers P. ser. Reticulata Croat [P. jefense, P. tysonii]
25b. Cataphylls persisting intact; stems markedly succulent P. ser. Pachycaulia Croat [P. basii]
22b. Pistils with ovules solitary (or sometimes 2, as in P. wilburii) in each locule; petioles frequently with purple ring at apex (P. subsect. Glossophyllum); blades elongate (P. ser. Glossophyllum) or ± ovate [P. subsect. Glossophyllum ser. Ovata].
26a. Blades mostly ± oblong and acute to narrowly subcordate at base; petioles frequently with a purple ring at apex
P. subsect. Glossophyllum(Schott) Engl.; P. ser. Glossophyllum (Schott) Croat [P. auriculatum, P. bakeri, P. brewsterense, P. correae, P. dolichophyilum, P. folsomii, P. granulare, P. immixtum, P. illgulatum, P. morii, P. pseudauriculatum; P. ubigantupense, P. utleyanum, P.wendlandii]
26b. Blades ovate to ovate-triangular, cordate to subcordate at base; petioles usually lacking a purple ring at apex
P. subsect. Glossophyllum; P. ser. Ovata Croat [P. cotonense, P. dominicalense, P. microstictum, P. smithii, P. straminicaule, P. sulcicaule, P. wilburii]
Note: for an
outline of the sectional classification of Philodendron subg. Philodendron
in Central America see apendix 3.