Willea truncata (G.M. Smith) D.M. John, M.J. Wynne & P. Tsarenko, 2014

John, David M., Wynne, Michael J. & Tsarenko, Petro M., 2014, Reinstatement of the genus Willea Schmidle 1900 for Crucigeniella Lemmermann 1900 nom. illeg. (Chlorellales, Trebouxiophyceae, Chlorophyta), Phytotaxa 167 (2), pp. 212-214 : 213

Willea truncata (G.M. Smith) D.M. John, M.J. Wynne & P. Tsarenko , comb. nov.

Basionym: Crucigenia truncata G.M. Smith 1920 . Bulletin of the Wisconsin Geological and Natural History Survey 57(1): 146, pl. 36, figs 7–9.

Nomenclatural synonym: Crucigeniella truncata (G.M. Smith) Komárek (1974: 38) .

Taxonomic synonym: Crucigenia apiculata var. truncata (G.M. Smith) Ahlstrom & Tiffany in Tiffany (1934: 69).

Requiring further investigation is Crucigeniella divergens (G.M. Smith) Fott (1981: 2) (basionym: Crucigenia divergens G.M. Smith (1926: 185)) , the type species of Crucigeniopsis ), a genus established by Hindák (1984: 267) and based largely on characters associated with reproduction. According to Hindák (1984: 268), Crucigeniopsis is distinguished from Crucigeniella by not producing autospores nor having ‘young’ cells lying in one plane within the coenobium, but rather the cells are in pairs produced by division at right angles to the long axis of the coenobium and initially lie at ‘an approximate right angle’ and the angle changing later but the cells never ‘fully in one plane, but pairs of cells were inclined to each other under a blunt angle’.

Only a molecular approach will unequivocally resolve relationships in the morphologically defined genera traditionally placed in the subfamily Crucigenioideae . The few strains of crucigenoid species examined so far have been placed in the Trebouxiophyceae, although in at least three different lineages ( Bock et al. 2013, Krienitz et al. 2003).