Lindley (1830) followed De Candolle in using the terms Monocotyledon and Endogenae interchangeably. Coverage of monocotyledon families is complete; other families are being added. About 10 Monocotyledon families include trees. Triteleia is a genus of monocotyledon flowering plants also known as triplet lilies. Corsia is a little-studied plant genus from the monocotyledon family Corsiaceae. Gymnostachys is a monotypic genus, of the monocotyledon plant family Araceae. Fritillaria orientalis is a Eurasian species of monocotyledon plant of the lily family. Cronquist merged the Liliaceae with the Amaryllidaceae, making this one of the largest monocotyledon families. It is a perennial monocotyledon with thick, soft leaves that form a rosette. There are 625 species, ten subspecies, and two varieties of monocotyledon assessed as endangered. There are 619 species, six subspecies, and four varieties of monocotyledon assessed as vulnerable. There are 16 species and two varieties of monocotyledon assessed as conservation dependent. Her scientific research focused on the monocotyledon group of flowering plants. There are 421 species, six subspecies, and five varieties of monocotyledon assessed as critically endangered. There are 1983 species, eight subspecies, and seven varieties of monocotyledon assessed as least concern.