GAHNA, in botany: A genus of the monogynia order, belonging to the hexandria class of plants. The calyx is an involucre with two or five flowers; the corolla is two-valved; the stamens six capillary and very short filaments; the antheræ linear, sharp-pointed at the apex, and as long as the corolla; there is no pericarpium: the seed is single and oblong.