Key to Series of Anthurium Section Pachyneurium
Blades usually oblanceolate to oblanceolate-elliptic, rarely oblong-elliptic or ovate-
cordate, usually drying brown, reddish brown, greenish-brown, or blackened, rarely
greenish or yellowish-green; primary lateral veins usually spaced and stout (generally
more than 3 cm apart), much more conspicuous than the interprimary veins (the latter
usually lacking); fruits usually red or purple to purplish in South America, often
orange in Costa Rica and Panama; found throughout the range of the section.
Blades usually oblong-elliptic to oblong-oblanceolate or elliptic, rarely oblanceolate,
usually drying green to yellow-green; primary lateral veins usually moderately weak,
usually closely spaced (generally less than 3 cm apart); interprimary veins usually
many, these almost as conspicuous as the primary lateral veins; fruits mostly orange,
sometimes purple; mostly endemic to Equador, also Narino, Columbia to Bolivia.
In general where interspecific pollinations have been attempted, the species of section
Pachyneurium are intercrossable. Several intersectional crosses have been made. Most Central
American members of Pachyneurium will interbreed as will most South American members of
the section but few Central and South American species crosses were viable (Croat, 1991).
Fruit set has been obtained in some intersectional crosses involving section Belolonchium
(A. umbrosum Liebm. x A. standleyi Croat & Baker; A. chiapasense Standi. x A. atropurpeum
Schultes & Maguire and A. lancetillense Croat (ined.) x A. luteynii Croat. Additionally
A. hookeri Kunth (unidentified section) is crossable with both A. crenatum and A. luteynii .
VI. POLYPHYLLIUM Engl. (Fig. 9 & 10)
This small but very natural section has only 2 species. It is characterized by having
very slender, wiry stems with adventitious roots along the internodes (restricted to the nodes
in other sections). In addition Polyphyllium is the only section of Anthurium which lacks
cataphylls, having instead sheathing petioles for protection of new growth. The section was
revised by Croat & Baker (1978) and includes A. flexile Schott and A. clidemioide Standley.
Only one taxon (A. flexile ssp. muelleri (Macbr.) Croat & Baker) has been counted with
2N = 60 chromosomes. The crossability of A. flexile to other Anthurium species is at present