Japan Flora: Tuber depressed-globose, about 3 cm. across; pseudostem about 30 cm. long; basal scalelike leaves 4, normal leaves 2, the lower one larger, with a petiole about 10 cm. long, the upper one smaller, with a petiole 4 cm. long; leaflets about 5, oblong, the terminal one petioluled, 11 cm. long; peduncle about 12 cm. long; spathe with the tube about 9 cm. long, 16 mm. across at base, ampliate above, the blade ovate to broadly so, bent nearly at right angles or more downward, about 8.5 cm. long, nearly as long as the tubular part, acuminate, dark purple; spadix-appendage clavate, 6 cm. long, purplish, thickened above, about 7 mm. in diameter at the verrucose apex.
Kyushu.
Allied to Arisaema serratum, but differs chiefly in the longer blade of the spathe bent forward horizontally.