[If] an ear [of standing grain] is in the reaped section [of the field], and its tip reaches to the standing [section] —- if it is cut together with the [other] standing grain, it belongs to the owner; but if not it belongs to the poor.  [If] an ear of leket became mixed with the stack [of grain], he tithes one ear of grain and gives it to him. Said R' Eliezer: But how can this poor person exchange a thing which has not yet come into his possession? Rather, he must grant to the poor man [ownership] in the whole stack, and then tithe one ear and give it to him.

A pile from under which the leket has not been gathered, whatever touches the ground belongs to the poor.  [If] the wind scattered the sheaves, we estimate how much leket it would normally yield, and he gives [that much] to the poor. R' Shimon ben Gamliel says: He gives to the poor according to the fall.