Although these morphological forms may be recognizable in the field, distinguishing these differences in herbarium specimens is often difficult, and there is much overlap occurs in expression of the characteristics supposedly defining infraspecific taxa. Numerous intermediate forms exist, including putative hybrid populations be tween the subspecies with 2n = 42 (D. G. Huttleston 1949, 1953). Given these problems and the sympatric ranges of the 'subspecies' recognized by previous workers, A. triphyllum is treated here as one highly variable species. In addition to the above variability within the Arisaema triphyllum complex, putative hybrid populations between A. triphyllum and A. dracontium also occur naturally (L. L. Sanders and C. J. Burk 1992). These plants do not produce mature fruits but do reproduce vegetatively.
Corm very acrid; lvs mostly 2, the petiole 3-6 dm at anthesis, sometimes later to 15 dm; lfls 3, acuminate, the terminal elliptic to rhombic-ovate, the lateral often asymmetrical; veins of the lfls parallel from the midrib to the marginal vein, connected by numerous anastomosing veinlets; peduncle 3-20 cm; spathe convolute below, expanded above and arched over the spadix, abruptly acuminate; spadix cylindric or barely clavate, yellow, blunt; fr 1 cm; 2n=28, 56. N.S. to N.D., s. to Fla. and Tex. Spring. Four vars., 3 in our range, the fourth (quinatum) southern:
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.