Leucojum
Leucojum is a small genus of bulbous plants native to Eurasia belonging to the Amaryllis family, subfamily Amaryllidoideae.[2][3][4] As currently circumscribed, the genus includes only two known species,[1] most former species having been moved into the genus Acis. Both genera are known as snowflakes.
Leucojum is a compound of Greek λευκος, leukos "white" and ἰόν, ion "violet". The spelling Leucoium is also used. Other common names include snowbell, dewdrop, and St. Agnes' flower.
Until 2004, the genus Leucojum was treated as including species now placed in Acis. Leucojum when narrowly circumscribed consists of only two species, Leucojum aestivum and Leucojum vernum. Compared to Acis, Leucojum has hollow rather than solid flower stalks (scapes), white flowers with green or yellow marks on both the inner and outer three tepals, flower stems (pedicels) at least as long as the spathes enclosing the inflorescence, and larger seeds, 5–7 mm (0.2–0.3 in) across. The marks at the tips of the tepals are quick way of distinguishing the genera when in flower. Like the related snowdrops (Galanthus), Leucojum has wider strap-shaped leaves rather than the usually narrowly filiform ones of Acis, 5–20 mm (0.2–0.8 in) wide in L. aestivum and up to 25 mm (1.0 in) wide in L. vernum.[3][5][6]
The genus Leucojum was erected by Carl Linnaeus in 1753,[1] initially for two species, Leucojum vernum and L. autumnale.[7] In 1759, he added the species L. aestivum.[8]
In 1807, Richard Anthony Salisbury illustrated two species in The Paradisus Londinensis. He initially used the name Leucojum autumnale for the plant illustrated in plate 21, but when discussing Leucojum pulchellum (now included in L. aestivum), illustrated in plate 74, Salisbury noted the differences between the two species, and considered them sufficient to move Leucojum autumnale into a new genus, Acis.[9][10] Although some botanists accepted the split between Leucojum and Acis, including Robert Sweet in 1829,[11] most did not; for example, Brian Mathew in 1987 placed all the species in Leucojum.[12] Acis was reinstated in 2004, after it was determined on morphological and molecular grounds that the broadly defined genus Leucojum was paraphyletic, with Acis and a more narrowly defined Leucojum being related as shown the following cladogram.[3]
Nine former members of the genus Leucojum, characterized by their narrow leaves, solid stems and unmarked flowers, are now placed in Acis, leaving only two species in Leucojum.[3]
