[The following] vegetables: cucumbers, pumpkins, melons, and kirbies; [and the following tree fruits:] apples and citrons, are obligated large and small. R' Shimon exempts citrons when they are small.  That which is obligated in [the case of] bitter almonds is exempt in [the case of] sweet [ones]. That which is obligated in [the case of] sweet [almonds] is exempt in [the case of] bitter [ones].