The holdfast is made up of numerous hairy cells and firmly secures the plant to a rock particle. The thallus consists of two layers, the cortex and the medulla. The upper part of the vegetative thallus has multiple apical meristematic zones, which are regions of cell division and growth. Sporangia are scattered throughout the thallus, located within the cortex, and typically have a conical shape. Occasionally, they divide to form four spores. Oogonia, the structures producing female reproductive cells, are found in small clusters within the cortex and can be either elliptical or conical in shape. Antheridia, which produce male reproductive cells, are densely distributed in clusters within the cortex and have a cylindrical form. These plants are typically brown or light brown in color.