This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Perennial herbs (some African species shrubby), ours with prostrate stems rooting and sending up tufts of long-petioled leaves at the nodes, together with 1-3 long-rayed umbellets of small white flowers, the true umbel sessile. Petiole-bases sheathing. Bracts of the invo-lucels 2-4, mostly prominent. Calyx-teeth none. Disk flat, or slightly concave. Styles filiform. Fruit somewhat flattened laterally, orbicular, reniform, or obcordate, rather prominently ribbed, the ribs mostly anastomosing; oil-tubes none. [Latin, diminutive of centrum, a prickle.]
About 20 species, of wide distribution, most abundant in South Africa. The following is the only one occurring in North America. Type species: Centella villosa L.
Stem creeping, glabrous or somewhat pubescent, 1'-6' long. Petioles 3'-12' long, sometimes pubescent; blades ovate, rather thick, very obtuse and rounded at the apex, broadly cordate at the base, not peltate, 1'-1 1/2 long, 9"-15" wide, repand-dentate; pedicels much shorter than the leaves, 1/2'-2' long; umbels capitate, 2-4-flowered, subtended by 2 ovate bracts; flowers nearly sessile; fruit 2"-2 1/2" broad, about \\" high, prominently ribbed and reticulated when mature.
In wet grounds, Maryland to Florida, west to Texas. Also in Bermuda, insular and continental tropical America, and Old World tropics. June-Sept.