1. In a plow including a wheeled frame adapted to be towed over the ground, a plow share comprising: a. a shaft carried for axial rotation by said frame, said shaft being horizontal but angled acutely to the direction of travel of said plow, and b. a helical flight of plate metal sharpened at its peripheral edge affixed concentrically to said shaft, said flight being disposed at an elevation relative to such frame such that the lower portion thereof is disposed beneath the ground level, the direction of twist of said flight being such that the relatively forward surfaces of the convolution thereof face generally in a direction angled forwardly from the axis of said shaft, said flight being uniformly concavo-convex in crosssectional contour radially to said shaft, the relatively forward surface thereof being concave and the relatively rearward surface thereof being convex, a generating line thereof at its intersection with a plane including the axis of said shaft being arcuately curved about a center of curvature lying substantially at the axis of said shaft, the angular extent of said generating line, measured from the axis of said shaft, being substantially equal to the horizontal angle at which said shaft is disposed to the direction of plow travel.