Genera: (a) Fixata: Isis, Gorgonia, Alcyonium, Spongia, Flustra, Tubularia, Corallina, Sertularia, Vorticella.
In a Volvox sphere, for with lime like Corallina among Red Algae.
To the law that no subsequent transverse division takes place in segments cut off from the apical cell, there seem to be two exceptions: first, the calcareous genus Corallina, in the pliable joints of which intercalated division occurs; and, second, the Nitophylleae, in which, moreover, median longitudinal division of axial cells is said to occur.
Melobesia callithamnioides gives rise to multicellular propagula; Griffithsia corallina is said to give rise to new individuals, by detaching portions of the thallus from the base of which new attachment organs have already arisen.
In Polysiphonia they cover the joints of the so-called leaves; in Chondria they arise on flattened disks; in the more massive forms they arise in patches on the ordinary surface; in a few cases (Gracilaria, Corallina, Galaxaura) they line the walls of conceptacle-like depressions.
Corallina sp., tetrasporangia with zonate arrangement of tetraauxiliary cells, the nuclei of which a and b retire to the wall.
Compare, for example, the blue-green Gloeocapsa with the green Gloeocystis, the red Batrachospermum with the green Draparnaldia, the red Corallina with the green Cymopolia, the green Enteromorpha with the brown Asperococcus, the green Ulva with the red Porphyra, the red Nemalion with the brown Castagnea, and so on.