Abstract text: In land plants, microfibrillar cellulose is synthesized by rosette cellulose synthesis complexes (CSCs) composed of Cellulose Synthase (CESA) or Cellulose Synthase-like-D (CSLD) proteins. Phylogenetic analyses indicate that these enzymes evolved from a common CESA/CSLD-like ancestor early in the diversification of the charophyte green algae (CGA). Rosette CSCs have been observed in all CGA species examined so far except Coleochaete, which was reported to have unique eight-particle CSCs. Although Coleochaetophyceae is the only major CGA lineage not represented by a genome sequence, transcriptome analyses have shown that Coleochaete expresses CSLDs, which seems inconsistent with the reported CSC morphology. Using a freeze-fracture specimen preparation method that promotes periclinal fracturing, we discovered that Coleochaete has rosette CSCs, contrary to previous reports and consistent with the presence of CSLDs in its genome. More broadly, members of the Coleochaetophyceae also have CESA/CSLD-like sequences, but no CESAs, based on analysis of 27 newly released Coleochaete and Chaetosphaeridium transcriptome assemblies. Genomic sequencing of Coleochaete CSLDs revealed numerous introns, in contrast to land plant CSLDs, which typically have 2-5 introns. Analysis of intron homology suggests a complex history of intron gain and loss in different lineages with implications for the divergence and functional specialization of CESAs and CSLDs.