Geniculate (alga)

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. The genuculae sometimes contain lignin.{{Cite journal | last1 = Martone | first1 = P. | last2 = Estevez | first2 = J. | last3 = Lu | first3 = F. | last4 = Ruel | first4 = K. | last5 = Denny | first5 = M. | last6 = Somerville | first6 = C. | last7 = Ralph | first7 = J. | title = Discovery of Lignin in Seaweed Reveals Convergent Evolution of Cell-Wall Architecture | journal = Current Biology | volume = 19 | pages = 169–175 | year = 2009 | doi = 10.1016/j.cub.2008.12.031 | pmid=19167225 | issue=2| doi-access = free }}

Genucila have probably evolved at least three times, evidenced by the three different modes of their formation.{{Cite journal | last1 = Johansen | first1 = H. W. | title = Patterns of Genicular Development in Amphiroa (Corallinaceae) | journal = Journal of Phycology | volume = 5 | issue = 2 | pages = 118 | year = 1969 | doi = 10.1111/j.1529-8817.1969.tb02589.x}}