About Epidendrum rigidum Jacq.
Epidendrum rigidum Jacq. is placed in the subgenus Epidendrum subg. Epidendrum Lindl. (1841) for three key morphological reasons: its sympodial stems do not thicken to form pseudobulbs, its stems are covered by the basal sheaths of its distichously arranged leaves, and its peduncle emerges from the apical leaf without being covered by any bract or sheath. The basal portions of the stems grow together to form a creeping rhizome, while the upper portions of the stems reach up to 20 cm (7.9 in) in length and can grow in an erect, horizontal, or hanging orientation. Its leathery leaves are ovate-oblong with an obtuse tip, measure 3–8 cm (1.2–3.1 in) long, and have a bilobed apex. Like other members of Epidendrum subsection Spathacea Rchb.f. 1861, its racemose inflorescence bears enlarged spathaceous floral bracts. The fleshy flowers are green, non-resupinate, and partially covered by large, axe-shaped dolabriform bracts. The sepals are ovate with an obtuse tip, measuring 5 mm (0.20 in) long, and the lateral sepals are larger than the dorsal sepal. The linear petals are also 5 mm (0.20 in) long. Like other species in the genus Epidendrum, the lip is adnate (fused) to the column all the way to the column's apex. Where the lip diverges from the column, it is heart-shaped, and the lip as a whole is ovate with an obtuse apex. The diploid chromosome number of E. rigidum has been determined as 2n = 40.
