Connor put together today's write-up:
Erythrina crista-galli is a member of the Fabaceae and is native to central South America. It is cultivated elsewhere, and has even been declared a noxious weed in parts of Australia. Its flower is the national flower of both Argentina and Uruguay (via Wikipedia). The epithet crista-galli means "crested comb" (from the Royal Horticultural Society who happened to feature this plant as Plant of the Month back in October), referring to the resemblance of the inflorescence to the comb of a rooster. This combined with erythros, meaning red, gives rise to one of the common names, the cockspur coral tree. Other names incude the cry baby tree and ceiba.
Like other plants in the Fabaceae Erythrina crista-galli associates with bacteria in a symbiotic relationship. The bacteria fix nitrogen for the plant in nodules found on the roots, and, in return for doing so, receive carbohydrates. This topic is a hot area of research because of the prospect of transferring this nodulation ability to other plants. In What Makes the Rhizobia-Legume Symbiosis So Special? (PDF), Hirsch et al. discuss the mechanisms by which this relationship takes place. It is thought that compounds produced by the Fabaceae called lectins play a crucial role in this process. Lectins are proteins produced by plant cells that bind to carbohydrates found on the surfaces of other cells (and are often very carbohydrate-specific). Their function is unknown but many speculate that they help plants defend themselves by recognizing invading cells. This cell-to-cell recognition also facilitates the establishment of an endosymbiotic relationship between a plant in the Fabaceae and a Rhizobium bacteria.