[1] Except for the isolated range of Marah gilensis (Gila manroot) in west-central Arizona and island populations (M. macrocarpus var.

major), all manroot species inhabit overlapping ranges distributed from Southern Canada to Northern Mexico.

Most have stout, scabrous or hairy stems, with coiling tendrils that enable them to climb up other plants; they can also grow rapidly across level ground.

The anthropomorphic common names "manroot" and "old man in the ground" derive from the swollen lobes and arm-like extensions of the unearthed tuber.

[citation needed] Marah species hybridize freely where ranges overlap and this, in addition to intra-species leaf and fruit variability, makes definite identification of specimens a particular challenge.

Considered as a separate genus, however, it includes six or seven species, some of them with well-defined varieties within them: Marah oreganus are used medicinally by Native Americans.

It is likely that the substance enters the fish's circulation through the gill arches where only a single-cell epithelium separates the water from the animal's red blood cells.