Apples, but discard the seeds. Only collect fruit from areas you know have NOT been treated with pesticides. Wash fruit thoroughly with warm water to remove dirt and debris. Do not use dish detergent or any type of sanitizer. These products can leave a residue.
Wild apples are generally quite a bit smaller than cultivated varieties.
They also tend to be somewhat harder and definitely more tart. Crab-apples can be used in place of domestic apples in many cooked recipes. Toxic Principle Cyanogenic glycoside, amygdalin. The list of poisonous plants on this web site does not necessarily include every poisonous plant that is known, or that might be found in an urban landscape or home. North Carolina State University does not advise eating any of the plants included in this web site.