1. Cissus trifoliata (L.) L. (marine vine, marine ivy)

C. incisa (Nutt. ex Torr. & A. Gray) Des Moul.

Pl. 579 a–d; Map 2713

Plants lianas (in Missouri, woody only toward the base), but sometimes dying back to the ground during cold winters and thus appearing herbaceous, with tuberous roots, often mostly with perfect flowers. Young stems somewhat angled and often somewhat succulent, pale green to green or reddish-tinged, glabrous. Older stems 2–6(–10 m) long, gray to less commonly brown, warty with orange to reddish orange lenticels, the pith white, not chambered. Tendrils at scattered nodes, sometimes few, occasionally also in the inflorescence, mostly unbranched, the tip slender. Leaves fleshy, the blades 1–7 cm long, ternately compound (rarely a few simple leaves present), ovate to triangular in general outline. Leaflets 1.0–6.5 cm long, ovate to obovate, spatulate, or narrowly fan-shaped, narrowed or tapered at the base (sometimes cordate in simple leaves), narrowed to sharply pointed tips, the margins coarsely and irregularly toothed, sometimes also with 1 or 2 lobes toward the base, glabrous or both surfaces very sparsely hairy. Inflorescences opposite the leaves or appearing terminal on branches, appearing as compound umbels, mostly longer than the leaves, flat-topped or somewhat dome-shaped, wider than long or slightly longer than wide, usually with 3–5 umbellate branches, the flowers in small umbellate clusters at the branch tips. Petals 4, free, 1.5–2.5 mm long, persistent and spreading at flowering, greenish yellow. Stamens 4. Nectar disc noticeable under magnification, cup shaped, fused to the ovary most of its length, the rim free, more or less entire. Style short, persistent at fruiting. Fruits 5–8 mm long, globose or obovoid, becoming shiny and black at maturity, sometimes with sparse small warty dots. Seeds usually 1 per fruit, 4.5–5.0 mm long, asymmetrically broadly obovoid, somewhat longitudinally angled along the inner side, brown. June–July.

Uncommon in southwestern Missouri (Florida to Arizona north to Missouri and Oklahoma; Mexico, Central America, South America, Caribbean Islands). Tops and ledges of dolomite bluffs.

Plants from the northern portion of the overall range of C. trifoliata were once separated as C. incisa by some authors (Steyermark, 1963; Brizicky, 1965), based on the presence of some simple leaves, more irregularly toothed leaflet margins, and slightly larger fruits, but most authors now consider them to represent merely a part of this variable species. In Missouri, the leaves of marine vine usually are deciduous and the stems tend to die back during cold winters, but farther south the leaves tend to be evergreen and the stems become much longer and woodier. Although it has been found in very different locations and habitats in the state, C. trifoliata possibly might be confused with the introduced Parthenocissus tricuspidata. The latter species differs in its branched tendrils with preformed adhesive discs at the tips, abundant aerial roots where stems climb up or over substrates, usually simple, 3-lobed leaves, and flowers with 5 petals and stamens.