''Hildenbrandia'' is a genus of thalloid
red alga
Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...
comprising about 26 species. The slow-growing, non-mineralized thalli take a crustose form.
''Hildenbrandia'' reproduces by means of
conceptacle
Conceptacles are specialized cavities of marine and freshwater algae that contain the reproductive organs. They are situated in the receptacle and open by a small ostiole.Boney, A.D. (1969). ''A Biology of Marine Algae''. Hutchinson Educational ...
s and produces
tetraspore
Tetraspores are red algae spores produced by the tetrasporophytic (diploid) phase in the life history of algae in the Rhodophyta as a result of meiosis.Jones, W.E. Revised and reprinted 1964. A Key to the genera of the British seaweeds.''Field S ...
s.
Morphology
''Hildenbrandia'' cells are around 3–5 μm in diameter and the filaments are around 50–75 μm in height.
The thallus comprises two layers: the
hypothallus
In true slime molds (myxogastria), lichens, and in species of the family Clavicipitaceae, the hypothallus is the layer on which the fruit body sits, lying in contact with the substrate. The word is derived from the Ancient Greek root ''hypó'' ("un ...
, which attaches to the rock, and the