Corallinales

(Silva & Johansen 1986: 250, emended according to Townsend et al. 1994)

Plants calcified and hard, of variable form, either semi-endophytic in other corallines, or growing on various substrates, or unattached; thalli multiaxial pseudoparenchymatous, or rarely of partially or largely unconsolidated filaments; merismetic cells (initials) either terminal, or intercalary and then producing one to several epithallial cells with partly calcified walls outwardly and other vegetative cells inwardly; walls of most other vegetative cells completely impregnated with calcite; primary pit plugs (where studied) containing an outer dome-shaped cap layer; cells of contiguous vegetative filaments often united by fusions or direct secondary pit connections; trichocytes often present.

Gametangial and tetra/bisporangial plants of similar organization; gametangia and sporangia borne within sori that are usually modified into conceptacles; gametangial plants monoecious or dioecious, gametangia borne in conceptacles that are uniporate; spermatangial systems simple to dendroid, borne on conceptacle floor and sometimes on walls and roof, carpogonial conceptacles with supporting (auxiliary) cells aggregated on conceptacle floor, each bearing 1-2 two-celled carpogonial branches; carposporophytes forming after presumed karyogamy and transfer of zygotic nucleus or its derivative(s) to supporting cell; supporting cells and sometimes other adjoining cells fusing to form a single fusion cell (possibly several in some Melobesioideae), producing short unbranched gonimoblast filaments each with a terminal carposporangium; tetra/bisporangia borne in unmodified sori or in conceptacles that are either uniporate or multiporate; tetraspores formed as a result of presumed meiosis followed by simultaneous zonate (Corallinaceae) or cruciate (Sporolithaceae) divisions of tetrasporocytes; sometimes replaced by binucleate or uninucleate bispores, the former presumably formed following meiosis and the latter following mitosis, populations reproducing apparently exclusively by uninucleate bispores sometimes common.

The original circumscription of the order was made by Silva & Johansen 1986: 250, when a single family, the Corallinaceae, was included. Verheij (1993) proposed the family Sporolithace for the genus Sporolithon with simultaneously cleaved, but cruciately divided, tetrasporangia or bisporangia borne in sori that are not modified into conceptacles. Verheij (1993) did not emend the order accordingly, but this was done by Townsend et al. (1994) with the erection of Heydrichia as the second genus of Sporolithaceae.

The main features deliniating the Corallinales are:

• thalli pseudoparenchymatous (i.e. based on the elaboration of filaments that give the impression of being organized into tissues)
• cell walls impregnated by calcium carbonate as calcite
• gametangia borne within conceptacles
• tetrasporangia or bisporangia borne within sori that may or may not be modified into conceptacles

Recognized families:

Corallinaceae

• simultaneously cleaved, zonately divided, tetrasporangia or bisporangia borne in conceptacles, that may be regarded as modified sori
  

Sporolithaceae

• simultaneously cleaved, but cruciately divided tetrasporangia or bisporangia borne in sori (singular sorus) that are not modified into conceptacles
  

Key references:

Silva & Johansen (1986), Townsend et al. (1994), Verheij (1993a), Woelkerling (1988).

Back to coralline page

Derek Keats,
updated 03/09/01