Cynipidae [gall on Q rubra is likely A cookii]
Quercus rubra, coccinea. MA. Sept-Oct. Soft, inanis center; purple-brown. Some are keeled on twigs
”- MT Thompson: (1915) An illustrated catalogue of American insect galls©
Reference: https://www.biodiversitylibrary.org/item/104098#page/64/mode/1up