Ceratozamia decumbens 知識
Rupicolous plants with globose to cylindrical trunks, partially or entirely subterranean, decumbent, branched, protected by reddish brown, persistent petiole bases and cataphylls, (9-)13.2(-20) cm long, (8-)10(-14) cm diam. (n = 5). Leaf cataphylls deltoid, stipulate, reddish brown, tomentose, 1.8-2.2 x 2.4 3.9 cm. Leaves (2 to)4(to 6), ascending to descending, pendulous in older mature plants, pinnate, vernation erect, reddish brown upon emergence, dark to olive green at maturity, forming an open crown, (70-)117 (-150) x (39-)55.9(-78) cm (n = 7); petiole and rachis linear to arching, terete with 2 parallel adaxial channels at level of leaflet articulations, unarmed or with few, distantly spaced, short stout prickles, pubescent at emergence, glabrous at maturity, petiole (22-)39(-69) cm (n = 7), base swollen, covered with beige tomentum, 1-2.6 cm wide, rachis (30-)49.8 (-93) cm (n = 6). Leaflets coriaceous, flat, 7 to 19 pairs, lanceolate, subfalcate, symmetrical or asymmetrical toward acuminate apex, leaflets wider and more asymmetrical in juvenile and young adult plants at times with a cleft toward apex, base attenuate, opposite to subopposite along apical and middle portion of leaf, alternate to subalternate along basal portion of leaf, margins subrevolute, entire, dark to olive green on adaxial surface, lighter green on abaxial surface, inserted flat, perpendicular to the rachis at proximal and middle portions of leaf, at slight angle toward distal portion, (21-)30.2(-38) x (2.4-)3.5(-4) cm (n = 11); articulation reddish brown becoming dark green at leaf senescence, (0.7-)0.79 (-1.1) cm wide (n = 8), (16 to)24(to 34) veins visible on adaxial surface (n = 14), intervein distance (0.1-) 0.15(-0.2) cm (n = 18), seedling eophylls 2, distance between leaflets (2.3-)3.8(-5) cm (n = 6). Microstrobili cylindrical, erect, green at emergence, dark green to light brown at maturity, (12-)15.5(-19) cm long, (2.3-)2.7(-3) cm diam. (n = 2); peduncle tomentose, light brown at emergence to brown at cone maturity, 2-14 cm long, 0.6-0.8 cm diam.; microsporophylls indeterminate, cuneiform, inserted spirally and perpendicular with respect to cone axis forming orthostichies, dark brown tomentulose, bicornate on distal surface, fertile portion covering 1/2 to 2/3 of abaxial surface excluding the horns, (0.9-)0.99(-1.2) x (0.6-)0.69(-0.8) cm (n = 8); horns straight to divergent, (0.2-)0.28(-0.4) cm, distance between horns (0.6-)0.67(-0.8) cm (n = 8); microsporangia numerous in sori of 2 to 3, dehiscence by longitudinal slit. Megastrobilus cylindrical or barrel-shaped, erect, olive green at emergence, dark green to brown at maturity, 11 cm long, 7.8 cm diam.; peduncle light beige tomentose, 3.8 cm long, 0.8 cm diam.; cataphylls long-triangular, stipulate, tomentose; megaspo rophylls indeterminate, peltate, spirally inserted along cone axis, (3.1-)3.3(-3.5) cm, including horns, distal face hexagonal to rhomboid, bicornate, dark metallic green with light beige tomentulum on margin, long axis (2.3-)2.5(-3.4) cm, short axis (1.1-)1.3(-1.5) cm (n = 6), horns diverging, (0.4-)0.6(-0.8) cm long, distance between horns (1.1-)1.2(-1.3) cm (n = 6). Seeds ovate-angulate, sarcotesta white when immature turning creamy beige to light brown at maturity, sclerotesta smooth, beige, with 8 to 12 visible rays radiating from the chalaza to the micropyle, (2.1-) 2.4(-2.6) cm long, (1.6-)1.7(-1.8) cm diam. (n = 6). Chromosome number 2n = 16.
A newly described species endemic to Veracruz, Mexico. Ceratozamia decumbens has affinity with C. morettii Vázquez Torres and Vovides, but differs in leaf morphology and leaflet habit as well as in the microsporangiate and megasporangiate strobili and trunk. It is considered part of the C. latifolia species complex, which includes C. latifolia Miquel, C. microstrobila Vovides and J. D. Rees, C. huastecorum Avendaño, Vovides and Castillo-Campos, and C. morettii. Ceratozamia decumbens is endemic on karstic hills in central Veracruz, Mexico. It grows on karstic rocks in subdeciduous tropical rainforest or bosque tropical subperennifolia sensu at an altitude of 712 m on shallow tropical rendzina soils.