A validly published name in botany, not necessarily legitimate or correct.
Petalonema alatum is a cyanobacterium (cyanophyte, cyanoprokaryote) described and drawn first time by the Scottish author Dugald Carmichael under the taxonomic name Oscillatoria allata in the book of Scottish cryptogamic flora edited by Greville in 1826 and later published under the still valid name Petalonema alatum by Miles Joseph Berkeley in 1833.