Philodendron radiatum var. pseudoradiatum (Matuda) Croat, stat. et comb. nov.
Philodendron pseudoradiatum Matuda, Revista Soc. Mex. Hist. Nat. 1: 96, fig. 8. 1950. TYPE: Mexico. Chiapas: Mun. Escuintla: Turquía, Salto de Agua, 8 Sept. 1947, Matuda 17787 (holotype, MEXU; isotypes, DS, NY, UC). Figures 8, 327--330.
Internodes 2--12 cm long, 1--2.5 cm diam.; cataphylls unribbed; petioles 28--78 cm long; blades shallowly lobed, the divisions near the middle of the blade extending less than 1/2 the way to midrib, 11--60 cm long, 11--42 cm wide; posterior lobes (8)12.5--25 cm long, (9)16.2--18 cm wide; basal veins 5(7--8) per side, with 0--1 free to base, posterior rib absent; primary lateral veins 3--5 per side. INFLORESCENCES 1 per axil; spathe 12--18 cm long; spadix 12.8--17 cm long; pistillate portion 4--4.5 cm long; pistils 1.6--2.2 mm long; ovary with sub-basal placentation; style similar to style type B.
The flowering phenology of Philodendron radiatum var. pseudoradiatum is still poorly known. Flowering collections are known only from January and September, but the flowering pattern is probably just poorly documented rather than bimodal.
Philodendron radiatum var. pseudoradiatum is endemic to Mexico, where it is known only from southwestern Chiapas, at 200 to 350 m elevation in "Selva Alta Perennifolia".
Philodendron radiatum var. pseudoradiatum is distinguished by its incised-lobate blades with the lobes divided less than halfway to the midrib. The typical variety generally has the blades incised more than three-fourths of the way to the midrib.
This taxon might be confused with P. dressleri, which also has leaf blades divided only about halfway to the midrib. That species differs in having much thicker stems (typically to 6 cm diam.), sharply 2-ribbed cataphylls, and by occurring in much drier areas where it loses its leaves during the dry periods. In contrast, P. radiatum var. pseudoradiatum has rather slender stems, unribbed cataphylls and occurs in mesic areas.
Until recently, Philodendron radiatum var. pseudoradiatum was represented by only two collections, Matuda 17787 and 18718, from the same locality. Several collections are noteworthy. Matuda 18045 consists of two sheets, one of which has a leaf lobed in much the same manner as the type, while the other has a leaf lobed to more than two-thirds of the way to the midrib. This may be an indication that the type of P. radiatum var. pseudoradiatum is merely an aberration in the degree of lobing for P. radiatum.
Another noteworthy collection is Croat & Hannon 63381 from Sierra de Soconusco, northwest of Mapastepec. It is perhaps also P. pseudoradiatum but has smaller and narrower leaves. It looks much like a hybrid between P. radiatum var. pseudoradiatum and some other species, but if so, it is not clear which other species might be involved in the putative hybrid plant.
Additional specimens examined.
MEXICO. Chiapas: Escuintla, Salto de Agua, 350 m, Matuda 18718 (MEXU, UC); Mpio. Mapastepec, Sierra de Soconusco, new unfinished road to Tuxtla Gutiérrez, 200 m, 15E31'N, 92E50'W, Croat & Hannon 63381 (CAS, CM, F, MEXU, MO, TEX.