An additional morphological criterion is presented to distinguish vegetative samples of the genera Yendonia and Mikamiella (Delesseriaceae, Rhodophyta). The undescribed earlier feature of Y. crassifolia is the presence of abundant lightrefracting cells in the tissues of the blades of both fertile and vegetative plants. This feature was never observed in Mikamiella, namely, in M. ruprechtiana. Additional data amending the description of the genus Yendonia are presented.