I can’t help but look at this photo and see a face on the cactus on the right, and he seems excited to see his taller date arrive in pearls. The cacti are Eulychnia acida and the “pearls” are the fruit of a Tristerix species, which is parasitizing the cactus. Eulychnia acida is a large tree-like cactus—growing as tall as 4 metres. It is native to the coastal deserts of Chile and Peru. Its long central spines can grow to 20 cm. Flowers are borne near the stem tips in summer, they remain open day and night.
I am not absolutely positive of the identity of the parasite. It is a Tristerix species, and I think it is Tristerix aphyllus. Tristerix aphyllus lives on only two species of cactus, Eulychnia acida and Echinopsis chilensis. Its seeds are distributed by the Chilean mockingbird, Mimus thenca. While the flowers and fruit are seen outside the cactus stem, the bulk of the parasite body may be found throughout the stem. The hummingbird pollinated flowers are a dazzlingly briliant red—yellow forms also exist. Unfortunately, I did not get a photo, but nice images are found on the Enciclopedia de la Flora Chilena.
A souvenir item found in tourist shops around the world is often made from Eulychnia acida. Rainsticks are traditionally made in Chile from the dried skeletons of the stems of the cactus. A length of stem is cut and cleaned. Spines from the cactus are then pushed through the wall of the hollow stem. Course sand is added and the stem is sealed. When turned from end to end, a sound reminiscent of rain is produced as the sand falls over the spines inside the hollow stem.
Reference: The Cactus Family. Anderson. Timber Press 2001.