Morphology and symmetry of the vegetative parts of Smilax auriculata (Smilacaceae)

Smilax auriculata produces a subterranean rhizome system and an aerial vegetative branching system. Three intergrading types of stems (types 1, 2, and 3) compose the aerial branching system; these types are identified primarily according to prickle concentration, but also differ from one another in additional ways. Type-3 stems are determinate and either proleptic or precocious. Between growing seasons a foliage leaf of a type-3 stem may subtend either a solitary vegetative bud (or an expanded vegetative branch) or an inflorescence superposed over a vegetative bud (or expanded vegetative branch). Occasionally, an inflorescence terminates a type-3 stem. Whereas, rhizomes exhibit solely scale leaves, the aerial vegetative branching system manifests scale leaves, transitional leaves, and foliage leaves. On many type-3 stems the foliage leaves become oriented skyward, by bending of their leaf sheaths and petioles. The aerial vegetative branching system manifests bilateral symmetry and mirror-image symmetry. The inflorescence is a pedunculate umbel. The peduncle culminates in a torus which bears a peripheral whorl of bracts, centripetally situated bracteoles, and pedicellate flowers. Type-1 stems exhibit numerous prickles, which vary from unbranched to branched and from solitary to basally connate in rows.