A geniculate habit, with reference to the red algae, is one in which the alga branches, tree-like, forming "fronds" that attach to the substrate with a holdfast.
Non-calcified "genicula" serve as "knees" or hinges between the calcified intergenicula.
The geniculate or non-geniculate form of algae was used to classify them; however either form has been convergently derived many times.
[1] Genucila have probably evolved at least three times, evidenced by the three different modes of their formation.
This Rhodophyta-related article is a stub.