Syngonium laterinervium Croat, sp.
nov. TYPE: Costa Rica, Puntarenas, Osa Peninsula, Corcovado National
Park within 2 km of park headquarters at Sirena, below 200 m, 8°29'N,
83°36'W, Liesner 2951 (MO-2588405, holotype).
Caudex scandens haud glaucus, internodiis 2-8 cm longis, 5-10 mm
diam.; foliorurn petiolus 10-20 cm longus, vaginatus praeter 1-3
cm distale, lamina trisecta, segmentum medium oblongum-ellip-ticum,
leviter inaequalaterum, (5.5-)8-17 cm longum, 2.3-5.5 cm latum,
apiee acuminatum, mucron-ulatum, basi acutum ad attenuatum, segmenta
lateralia (5.2-)9-14 cm longa, 2.5-4 cm lata, oblonga-elliptica,
inaequalatera basi auriculata; folia venis lateralibus utroque latere
4-6, nervis parvis vix prominioribus, subangulo ca. 10-20°.
Inflorescentia pedunculo 4.5 cm longo, in axilla solitarius; spathae
tubus ca. 3.5 cm longus, 1.2 cm diam., anguste ellipticus, extus
viridis pallidus; spathae lamina ca. 5 cm longa, alba.
Juvenile stages not seen. Adult plants with scandent stems, much
internodes 2-8 cm long, 5-10 mm wide, green, drying light brown,
the periderm often flaky in small patches; petioles 10-20 cm long,
sheathed except for the last 1-3 cm, the sheath free-ending and
narrowly acute at the apex, those subtending inflorescences much
broader in the lower half, the portion between the petiole and blade
flattened adaxially; blades trisect, the leaflets overlapping or
not distinctly free from one another; median leaflet oblong-elliptic,
somewhat inequilateral, acute and cuspidate to narrowly acuminate
at the apex, obtusely cuneate to attenuate at the base, (5.5-)8-17
cm long, 2.3-5.5 cm wide; lateral leaflets oblong-elliptic, very
inequilateral, narrowly acute to attenuate on the inner margins
at the base, conspicuously auriculate on the outer margins at the
base, usually joining the petiolule at ca. 90° angle, the petiolule
4-10 mm long, canaliculate on upper side, the margin continuous
with the margin of both the median and lateral
leaflets, the auricles about as long as or longer than broad, 12-28
cm long, oblong to triangular, rounded at the apex; midrib weakly
sunken on upper surface, raised beneath; primary lateral veins 4-6
pairs, slightly more conspicuous than the smaller lateral veins,
all the veins below clearly visible, departing the midrib at ca.
70° angle, spreading almost straight to the collective vein;
collective veins 2 or 3, the principal one 2-5 mm from the margin.
Inflorescences solitary; peduncle ca. 4.5 cm long,
ca. 3 mm diam., erect at anthesis; spathe ca. 8.5 cm long, spathe
tube narrowly ellipsoid, ca. 3.5 cm long, 1.2 cm diam., the outside
pale green; spathe blade elliptic, ca. 5 cm long, acuminate at the
apex, white; spadix ca. 7 cm long;
pistillate portion of the spadix 1.8 cm long, ca. 9 mm diam., the
flowers irregularly hexagonal, the stigmas flat at the apex, 1.5-2
mm diam.; staminate portion of the spadix ca. 5 cm long, clavate,
ca. 1.5 cm diam. at the broadest point in the upper V3, the fertile
staminate flowers mostly rhombic to sometimes irregularly hexagonal
at the apex, the surface minutely rugose, the margins weakly crenate.
Infructescences unknown. Fig. 16.
DISTRIBUTION: Syngonium laterinervium is known from
southwestern Costa Rica and northwestern Panama in tropical wet
forest life zones in the region surrounding Golfo Dulce, at elevations
ranging from near sea level to 450 m.
It is most easily confused with S. hoffmannii but differs
in having the lateral veins departing the midrib at no less than
ca. 70° angle and in having the primary lateral veins only slightly
more prominent than the lesser lateral venation. Syngonium
hoffmannii has at least the lower primary lateral veins
departing the midrib at a much sharper angle (ca. 50°), and
much more conspicuous than the minor lateral veins (drying much
darker than the surface).
The species was first collected by Paul Alien in 1951 and was not
collected again until 1973. According to Alien 6035 the plant was
a branching vine forming dense masses on the trunks of large trees
in climax forest.
Flowers have been found in July.
COSTA RICA: PUNTARENAS: Corcovado National Park,
Liesner 2951 (MO); Esquinas Forest, Alien 6035 (F, GH, US).
PANAMA: CHiRioui: West of Puerto Armuelles, Busey 605 (MO).