Abstract
Nitella singaporensis is described as a new species based on specimens from Singapore. This study provides detailed examination of the fully mature plant. The species is described here using multiple methods including scanning electron microscopy and molecular phylogenetics. Re-examination of the type specimen of N. caespitosa, the most similar species, will be necessary for future studies. The particular oospore surface pattern visible using scanning electron microscopy, which does not equate to previously described features, is recorded here for the first time in the genus Nitella. Nitella singaporensis is placed in section Gioallenia of subgenus Tieffallenia according to its morphological and phylogenetic affinities. The presence of adventitious cells at base of the branchlets and significance of this trait for Nitella taxonomy is discussed.