This account reviews past and present concepts of the genus, the systematic position of the genus and its family, and a detailed taxonomic account of the 30 Indian species in the light of modern taxonomic parameters, with a description of morphological diversity, geographical distribution, supplemented with plates, tables and maps. All the figures are drawn by one of the authors (GA).

The subgenus Aphanolejeunea is mainly characterized by the fragile nature of the plants, distantly arranged leaves often with dimorphic lobules, Aphanolejeunea-type of lobular teeth and Aphanolejeunea-type branching. The subgenus Chlorolejeunea is mainly characterized by a massive type of stem anatomy (17 + 7) in contrast to the highly reduced stem anatomy (5 + 1) of the genus. The subgenus Cololejeunea is mainly characterized by well developed dorsal papillosity on the leaf-cells.

The subgenus Leptocolea is mainly characterized by the crenate or dentate leaf-lobe margin and leaf-cells being usually without dorsal papillosity (when present, restricted to marginal leaf-cells or younger portion of the plants only). The subgenus Pedinolejeunea is mainly characterized by dimorphic leaf-cells (chlorophyllous and hyaline: rectangulate, elongated or linear-flexuose) and ligulate lobule with apical hyaline papilla.

The subgenus Taeniolejeunea is mainly characterized by the presence of ocelli, forming a vitta.

This work incorporates a review of the past and present status of Cololejeunea, the previous work done by different authors, taxonomic parameters used for delimiting the species, morphological descriptions of the genus Cololejeunea, its subgenera as well as species and keys to segregate subgeneric groups and species. It also includes relevant synonymy, characteristics of the species, full references to the specimens examined, geographical distribution, notes on ecology and a discussion to highlight the specific differences, affinities and elucidation of those features which have not been taken into consideration so far. The work is supplemented with 44 plates of line drawings, 9 photoplates, including LM & SEM photographs. Besides, three tables, showing the past and present status of genus Cololejeunea, its subgenera as well as its Indian species have been provided. An additional table showing the distribution of 30 species within the Indian subcontinent along with their habitats has also been provided. Cololejeunea is a tropical-subtropical genus and preferentially grows on living leaves. Other habitat preferences are bark, rock and earth. In the Indian subcontinent, southern India is the richest territory with 23 species followed by the east Himalayan territory with 17 species and then the west Himalayan territory with two species. Central India has the poorest Cololejeunea flora, with only single species, (C. latilobula) which is also known from southern India, eastern and western Himalayas.