high density is concentrated along the floor of the trough from being drawn into the fan by way of development a transverse intermediate baffle 29 is provided spaced upstream of the baffle 27 the baffle 29 depends from the sieve 24 it can readily be replaced to vary for example its height free ends of the baffles 27 and 29 preferably overlap when seen in axial projection the upstream baffle will deflect grain which has become airborne to prevent such airborne grain from being drawn into the fan furthermore the baffles 27 29 cause the auxiliary air flow stream to become circuitous to be directed momentarily generally into an auxiliary grain exit 39 which will be described hereinafter the baffle 29 is advantageously opposite to a centre of the auxiliary grain exit 39 it is to be appreciated that because the sieve 24 and the trough 34 are merely arcuate or convex and not circular the air flow stream 37 moves in a relatively narrow channel thus making it more effective alternatively requiring less air to be moved in use harvested crops in the form of ears pods or the like fall under gravity into the hopper 28 to be transported obliquely upwardly as indicated at 44 into the threshing zone 16 by means of the transport means 22 in the threshing zone 16 the ears pods or the like are threshed to liberate grain.