"She could very well pass for forty-three in the dusk with the light behind her" - Gilbert and Sullivan

Photographed in the conservatory at Manito City Park, Spokane, Washington. I have no idea what cactus this is and would like help identifying it. The park is one of the most beautiful city parks I've ever seen, but we were visiting our handicapped son and had only limited time there. The quotation is from Gilbert and Sullivan's "Trial by Jury."