A cotyledon is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." Botanists use the number of cotyledons present as one characteristic to classify the flowering plants (angiosperms): species with one cotyledon are called monocotyledonous ("monocots"); plants with two embryonic leaves are termed dicotyledonous ("dicots"). Many orchids with minute seeds have no identifiable cotyledon, and are regarded as acotyledons. The Dodders also lack cotyledons, as does the African tree Mammea africana (Calophyllaceae). A very small number of Dicots have more than two cotyledons, with perhaps Psittacanthus schiedeanus being the most extreme, having up to twelve.