The blades consist of one or two rigorously coplanar layers of cells. The cells are more or less evenly distributed within the layer and are encased in a stiff mucilage. The cells are uninucleate and contain one or two stellate plastids with a conspicuous pyrenoid in the exact center of the plastid - the uninitiated often confuse the pyrenoid with the nucleus. Cells at the base of the blade produce rhizoids, which affix the blade to the substrate. Microscopic Porphyra consists of branched filaments with cells 2-10 micrometres in diameter and usually many times longer than broad.
Pit connections are present between cells.
Pyrenoids are inconspicuous in or absent from the plastids. Conchocelis filaments in nature are always found boring into a calcium carbonate substrate. For example, the conchocelis of many intertidal species resides in the shells of living intertidal barnacles.