Walk-behind lawn mowers have been commonly equipped with a rear grass bag or a discharge chute.  In most cases, these items are interchangeable.  The rear grass bag arrangement has been beneficial because the rear grass bag allows the operator to maneuver more closely to the trees, hedges and other lawn obstacles.  Additionally, the rear grass bag allows the weight of the accumulated grass clippings to be more evenly supported by the rear wheels of the lawn mower, rather than to weigh down a single side as in a side discharge mower.  Thus, the rear grass bag arrangement allows for more even cutting of the grass. 
Often, in a mower with a rear grass bag arrangement, the rear grass bag attachment may be removed and a discharge chute may be installed in its place.  Such a discharge chute commonly expels the grass clippings to the side.  In a mower of the rear grass bag type, the exit of the grass clippings from the mower housing is generally provided at the rear of the housing.  Thus, when the rear grass bag is attached, the clippings are directly projected into the rear grass bag.  When the side discharge chute is attached, instead of the rear grass bag, the clippings are directed into the chute which in turn discharges the clippings to the side.  Such side discharge chutes are commonly shaped in the form of a bent tunnel for sidewardly discharging the grass clippings. 
Such side discharge chutes, however, are inconvenient in that, because of their shape in the form of a bent tunnel, the clippings are sometimes expelled onto the grass in the form of a windrow as they are being discharged from the chute.  Such windows, or the like, extend the time required for the grass clippings to dry out, and is more unsightly when the clippings are not raked up. 
The discharge chute provides a path for the cut grass clippings to travel through and to be directed back to the ground.  However, as the grass becomes heavy and/or wet, it becomes more difficult for the air flow to carry the grass clippings away.  Basically, the air separates from the grass and a row of cut grass forms right below the exit from the discharge chute.  In the conventional designs the maximum air flow exits towards the top of the discharge opening.  This air flow pattern allows the air and grass to separate prior to exiting the chute and causes the wind rowing (the formation of grass clippings along a line) of the grass. 
According to the instant invention, the velocity of the air exiting the discharge opening is generally less.  The air becomes more turbulent and it mixes more with the grass clippings before leaving the discharge chute.  The greater air velocity occurs generally in the central portion of the discharge opening, thus prolonging the mixing of the air and grass clippings until the grass has exited the chute.  The extra mixing action spreads the grass further and more uniformly.