British Phycological Journal

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A reappraisal of the order Corallinales (Rhodophyceae)

Paul C. Silva & H. William Johansen

To cite this article: Paul C. Silva & H. William Johansen (1986) A reappraisal of the order Corallinales (Rhodophyceae), British Phycological Journal, 21:3, 245-254, DOI: 10.1080/00071618600650281 To link to this article: https://doi.org/10.1080/00071618600650281

Published online: 23 Feb 2007.

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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=tejp19 Br. phycol. J. 21:245 254 1 September 1986

A Reappraisal of the Order Corallinales (Rhodophyceae)

By PAUL C. SILVA

Department of Botany, University of California, Berkeley, California 94720, USA

and H. WILLIAM JOHANSEN

Biology Department, Clark University, Worcester, Massachusetts 01610, USA

Articulated and non-articulated coralline alga e were brought together in the family Corallinaceae in essentially its present-day circumscription by Decaisne in 1842. Since that time, this family has been perceived as one of the most distinctive assemblages of Rhodophyceae. Alignment of families of into orders based on criteria that today are considered to reflect natural relationships extends back only as far as 1892, when Schmitz presented a scheme founded largely on details of the female reproductive system and gonimoblast development. In that scheme, the Corallinaceae occupied an anomalous position in the Cryptonemiales. While attempts have been made to modify the definition of the Cryptonemiales to accommodate the Corallinaceae more comfortably, an ongoing accumulation of information supports the segregation of that family into its own order. At least three previous authors have adopted the taxonomic concept of the Corallinales, but the name has not yet been validated. In the present paper a Latin diagnosis is provided. Diagnostic characters of the Corallinales include the following: (1) walls of most vegetative cells are impregnated with calcite; (2) meristems are often intercalary and covered by a layer of cells; (3) plugs of primary pit-connections have two-layered, dome-shaped caps; (4) reproductive structures are produced in roofed conceptacles in all genera but one; (5) tetrasporocytes usually undergo simultaneous zonate division; (6) post-fertilization events involve a cluster of procarpial filament systems.

HISTORICAL BACKGROUND lated forms had to be distinguished from corals. Second, the circumscription of For more than a century the coralline had to be shorn of unrelated algae have been perceived by taxonomists as calcified algae (the red alga Galaxaura and one of the most distinctive assemblages of various siphonous Chlorophyceae). Third, Rhodophyceae. Prior to the period 1842- agreement had to be reached on the close 1853, when this perception was solidified, relationship between articulated and non- the taxonomic history of this assemblage articulated forms. As might be expected, the followed three interrelated lines. First, latter, being rocklike or coralloid, were agreement had to be reached on the nature accepted as plants less readily than the of corallines--whether they were plants or former. animals, or organisms intermediate between The two groups, articulated and non- animals and plants (zoophytes), or articulated, were brought together in organisms intermediate between minerals essentially their present-day circumscriptions and plants (lithophytes). Those with arti- by Decaisne (1842a, pp. 359, 365; 1842b) culated fronds had to be distinguished from and Chauvin (1842, pp. 109, 127), who sessile animals with flexible bodies, especially assigned them to the Corallinaceae, a family hydroids and bryozoans, while non-articu- established by Lamouroux (1812, p. 185,

0007-1617/86/030245 + 10 $03.00/0 © 1986 British Phycological Society 1

Published online 23 Feb 2007 246 P.C. Silva and H. W. Johansen

"Corallineae") to include Galaxaura and (1837) and Lithothamnium Philippi (1837)]. calcified siphonous Chlorophyceae as well as Subsequent authors generally have Amphiroa, Corallina, Jania, and Melobesia. recognized only one family, Corallinaceae. Decaisne's belief that reproductive structures Exceptions include J. E. Gray (1864, p. 22) were of primary taxonomic significance led and his nephew S. O. Gray (1867, p. 133), to success in sorting out the true corallines, who recognized the family , which he placed in his Algae based on Hapalidium Kiitzing (1843), a Choristosporeae alongside other genera now genus said to differ from the Corallinaceae assigned to the Florideophycidae. Lack of s. str. by its lack of calcification. Hapalidium knowledge regarding reproduction in calci- roseolum Kfitzing, the type of the genus, is in fied siphonous Chlorophyceae, however, led fact slightly calcified and is conspecific with to the dispersal of these genera between two Melobesia membranacea (Esper) Lamouroux, major categories, Algae Zoosporeae and according to Chamberlain (1983, p. 300). Algae Aplosporeae. A detailed account of Much later, Hylander (1928, p. 173), in a the taxonomic vicissitudes of coralline algae flora of Connecticut, assigned was given by Decaisne in the second part of Lithothamnium and Melobesia (and his thesis (1842b). presumably all other non-articulated Johnston, a British contemporary of corallines) to the Squamariaceae Decaisne, offered a contrasting treatment in (= Peyssonneliaceae). In recent years rather which the family Corallinaceae was reserved elaborate classifications have been proposed for articulated forms (erroneously including within the Corallinaceae (e.g., Cabioch, Halimeda), while non-articulated forms were 1971, 1972; Lebednik, 1977; Johansen, segregated as a distinct family, 1981). Nulliporaceae Johnston (1842, pp. 205, 231, 254, "Nulliporidae"). (Nullipora Lamarck TAXONOMIC POSITION OF (1801) is a superfluous name for Apora CORALLINACEAE Gunnerus (1768), the oldest available name for a genus of non-articulated corallines. Alignment of families of red algae into Johnston's recognition of four species of orders based on criteria that today are Nullipora in the British flora was purely considered to reflect natural relationships academic, however, as made clear by the extends back only as far as 1892, when following passage: "I believe that the Schmitz presented a scheme founded largely Nullipores are endowed with life, and with a on details of the female reproductive system vegetative growth, but that they are not and gonimoblast development. The four species. They are, to my conviction, merely orders of subclass proposed by the calcareous basis of Corallina officinalis Schmitz (Nemaliales, Gigartinales, modified by external circumstances, and Rhodymeniales, and Cryptonemiales, in that hindered from passing through the stages of sequence) are presently accepted, but with its normal developement"). Johnston's numerous modifications of varying account of the taxonomic history of the consequence, most notably the segregation corallines (Johnston, 1842, pp. 207 215, of the Ceramiales from the Rhodymeniales 233 237) is couched in colourful language by Oltmanns (1904, p. 683) and the segrega- lightly brushed with cynicism. tion of the Gelidiales from the Nemaliales by Non-articulated corallines were also Kylin (1923, p. 132). (The ordinal name placed in a distinct family by Kfitzing, who, Ceramiales should be credited, however, to however, employed the family name N~igeli, 1847, pp. 126, 253, "Ceramiaceae".) Spongitaceae Kfitzing (1843, pp. xxiii, 382, Among subsequently segregated orders, 385, "Spongiteae"). [Spongites was Nemastomatales Kylin (1925) and proposed by Kfitzing in 1841 to apply to a Sphaerococcales Sj6stedt (1926) have been genus that combined Lithophyllum Philippi abandoned (at least temporarily), while Reappraisal of the order CoraUinales 247

Bonnemaisoniales J. Feldmann et G. cells in a sorus become connected to form a Feldmann (1942), Acrochaetiales J. fusion cell from which gonimoblasts arise. Feldmann (1953), and Chaetangiales Whether ooblast filaments are involved was Desikachary (1963) have received negligible not known by Schmitz and remains a support. The recently proposed Palmariales controversial issue (Johansen, 1981, p. 105). Guiry et D. Irvine (in Guiry, 1978) is likely In deciding which of Schmitz's orders to fare better because of the very distinctive would most comfortably receive the life history exhibited by Palmaria and Corallinaceae, it is essential to clarify the Halosaccion (van der Meer & Todd, 1980; meaning of the term "procarp". This term van der Meer, 1981). Only the passage of was applied by Thuret & Bornet (1878) to time will reveal the fate of the fledgling the female reproductive system of Batrachospermales and Hildenbrandiales, Ceramiaceae and Rhodomelaceae at the both proposed by Pueschel & Cole (1982). stage of readiness for fertilization. It In addition to the recognition of new orders, included the supporting cell, the carpogonial there has been considerable movement of branch, and the auxiliary cell. Schmitz genera and families from one order to (1883) applied the term broadly to another, especially between the Gigartinales "Gruppen von Carpogon/isten und and the Cryptonemiales. Auxiliarzellen, die als selbstfindiges Ganzes Schmitz (1892) gave the following am Thallus der Mutterpflanze such characterization of the orders of Florideae: abheben..." Later, Schmitz (1892) Nemaliales, gonimoblast developing extended the definition to include the pairing directly from the zygote. of a carpogonial branch with an auxiliary Gigartinales, carpogonial filaments and cell mother cell (as in the Ceramiales). Still auxiliary cells usually paired to form later (in Schmitz & Hauptfleisch, 1897, procarps, seldom scattered in the p. 538), he referred to "Procarpiencon- thallus; the zygote connecting with the ceptakeln" in the Corallinaceae. Considering auxiliary cell by means of an ooblast Schmitz's broad definition of "procarp", we filament that is usually short; gonimo- are puzzled that he treated the Corallinaceae blast developing inwardly. as the last of seven families in the Rhodymeniales, carpogonial filaments and Cryptonemiales rather than as a member of the mother cells of auxiliary cells paired the Gigartinales. to form procarps; the zygote connecting The uncertain boundary between the with the auxiliary cell by means of a Cryptonemiales and the Gigartinales, mani- short ooblast process; gonimoblast fest in Schmitz's overlapping characteriza- developing outwardly. tions, was addressed by Kylin (1923). In Cryptonemiales, carpogonial filaments and redefining the various floridean orders, auxiliary cells scattered in the thallus; Kylin emphasized the time of differentiation the zygote sending through the thallus of auxiliary cells and the presence or absence more or less long, frequently branched, of procarps. As proposed by Schmitz (1883), ooblast filaments that fuse with "Auxiliarzellen" could be either nutritive or auxiliary cells; gonimoblast developing generative in function. Distinguishing either inwardly or outwardly. between the two types, Kylin noted that in In the Corallinaceae, two-celled carpo- both Cryptonemiales and Gigartinales gonial filaments are clustered in sori (within generative auxiliary cells were cut off prior conceptacles) and the auxiliary cells are to fertilization. Kylin also wrestled with the supporting cells of functional or in- concept of the procarp, trying to decide on a completely formed carpogonial filaments or taxonomically meaningful definition. He corresponding cells of adjacent sterile (and agreed with Schmitz that procarps were presumably homologous) filaments. Follow- lacking in the Cryptonemiales and that the ing fertilization, many, if not all, auxiliary Corallinaceae belonged to that order. As if 248 P.C. Silva and H. W. Johansen

to defuse criticism for assigning a procarpial tion between his characterization of the family to a non-procarpial order, Kylin Cryptonemiales as non-procarpial and the adopted a restrictive interpretation, stating assignment to this order of the that the association of carpogonial filaments Gloiosiphoniaceae, considered by Schmitz to and auxiliary cells in a sorus could not be be procarpial. The carpogonium and considered a procarp in the sense that the auxiliary cell are part of a single accessory term was applied in the Gigartinales, filament system, but Kylin argued that in Rhodymeniales, and Ceramiales because of Gloiosiphonia, at least, there was no proof the imprecise relationship: the zygote that the ooblast filament connected solely ultimately connects with several auxiliary with a predetermined auxiliary cell to the cells, apparently at random, rather than with exclusion of nearby auxiliary cells. He a predetermined auxiliary cell. Kylin con- admitted, however, that true procarps were sidered the Corallinaceae to represent the found in Thuretella, another member of the highest point of development within the family. As for the Gigartinales, Kylin Cryptonemiales. included in this order only procarpial forms. As the morphological details of more and He invoked a secondary character to more floridean genera became known distinguish them from members of the (largely through his own research), Kylin Cryptonemiales: in the former the gonimo- realized that the presence or absence of blast was said to have a sterile framework, procarps was inadequate as a primary while in the latter all except perhaps the ordinal character. Striving for a more lowermost cells become carposporangia. satisfactory classification, he applied a new Kylin's concept of the Nemastomatales was criterion, namely, whether the auxiliary cell murky. He merged the recently proposed is a member of a special accessory filament Sphaerococcales (Sj6stedt, 1926) into the or of an ordinary vegetative filament. This Nemastomatales, which thus came to decision could be made readily among those include both procarpial and non-procarpial algae in which the auxiliary cell was not a forms. The difference between procarpial part of the carpogonial filament system (i.e. Nemastomatales and Gigartinales was said non-procarpial forms), and Kylin (1925) by Kylin to be that in the former the fertile divided the Cryptonemiales into those with filament system was vegetative while in the auxiliary cells of the first type (Crypto- latter it was accessory. At this time Kylin nemiales s. str.) and those with auxiliary was inconsistent, recognizing two orders cells of the second type (Nemastomatales). characterized by accessory auxiliary cells After studying the morphology of 28 (procarpial Gigartinales and non-procarpial additional species of Florideophycidae, Cryptonemiales) but only one order Kylin (1928) gave a lengthy review of the characterized by vegetative auxiliary cells classification of this group. Still concerned (Nemastomatales, with both procarpial and with the taxonomic significance of the non-procarpial forms). procarp, he adopted a broad definition to Kylin (1930), by transferring the Endo- accommodate several variant situations that cladiaceae, a procarpial family, from the had recently become known. Again, how- Gigartinales to the Cryptonemiales, ever, he supported his contention that true continued to shift the primary ordinal procarps were generally lacking in the character from the presence or absence of Cryptonemiales. He termed the clusters of procarps to the accessory or vegetative carpogonial filaments and auxiliary cells in origin of the auxiliary cell. The shift was the Corallinaceae "zusammengesetzte completed by Kylin in a summary appended Prokarpien" in contrast to "einfache to his monograph of the Gigartinales (Kylin, Prokarpien". (He also applied "zusammen- 1932), where he provided a key to the orders gesetzte Prokarpien" to the Gelidiales.) of the Florideae. He transferred the Kylin tried further to reduce the contradic- Kallymeniaceae, in which both procarpial Reappraisal of the order Corallinales 249

and non-procarpial forms occur but in which who have recognized an order Corallinales, the fertile filament systems are clearly but none gave either a discussion or a accessory, from the Gigartinales to the diagnosis. Funk (1927), Hylander (1928), Cryptonemiales. This decision would have and J. Feldmann (1931) explicitly or left the Gigartinales with only one family, implicitly included the Squamariaceae the Gigartinaceae (at that time including the (correctly known as the Peyssonneliaceae) Phyllophoraceae), but Kylin reversed his and the Hildenbrandiaceae along with the earlier opinion (Kylin, 1928, 1930) that in Corallinaceae in the Corallinales. Gigartina and Phyllophora the auxiliary cell Non-coralline genera assigned to the was accessory, and thus eliminated the chief Corallinales by these authors include character separating the Gigartinales from Cruoria, Cruoriopsis, Cruoriella, the Nemastomatales. He therefore merged Peyssonnelia, and Hildenbrandia. We do not these two orders, changing the narrowly think that the relationship between any of circumscribed Gigartinales of his earlier these crustose red algae, which are generally papers to the broadly circumscribed order uncalcified, and the corallines is sufficiently familiar to us today. close to warrant placement in the same Despite Kylin's tortuous restructuring of order. Schmitz's original orders, the boundary In addition to these unequivocal but between the Cryptonemiales and the invalid uses of the name Corallinales, there Gigartinales, as presented in Kylin's final are three apparent uses that should be work (1956), is not unequivocal. Problem discussed. (To our knowledge Corallina is areas include the definition of "accessory", the only generic name among corallines that the interpretation of clusters of reproductive has served as the basis for an ordinal name.) systems (sori or nemathecia), the interpreta- Names applied to taxa designated as orders tion of auxiliary cells that are an integral prior to about 1880 seldom can be con- part of the carpogonial branch system, and sidered ordinal in the sense prescribed by the the interpretation of situations in which the International Code of Botanical Nomen- gonimoblast arises from some structure clature (Voss et al., 1983). The hierarchy of other than the auxiliary cell (for instance, taxa and the accepted designations of their from a connecting filament). Various authors ranks are set forth in Art. 3. Both the (e.g., Papenfuss, 1951; Lebednik, 1977) have concept of individual hierarchical ranks and offered refinements, but the equivocation the terms applied to them were in a state of remains. In the most recent review of the flux in the 19th century (Silva, 1980). problem, Kraft & Robins (1985) accept the Deviation from the prescribed ranking of segregation of the Hildenbrandiales and taxa is outlawed (Art. 33.4) except for a Corallinales from the Cryptonemiales and single misplaced term in a single mycological merge the remainder of that order into the work (Art. 33.5). Deviation from the pre- Gigartinales. While we do not agree with the scribed designations of properly ranked taxa, merger, we concur in the opinion of those on the other hand, is accommodated by two authors that elevating the Hildenbrand- rather subjective rules. Article 17.2 states iaceae and Corallinaceae to the rank of that "Names intended as names of orders, order renders the Cryptonemiales a more but published with their rank denoted by a homogeneous group. term such as 'Cohors', 'Nixus', 'Alliance', or 'Reihe' instead of ordo are treated as having been published as names of orders." PREVIOUS RECOGNITION OF THE Article 18.2 states that "Names intended as ORDER CORALLINALES names of families, but published with their As the title of this paper suggests, we are rank denoted by one of the terms order not the first to propose a separate order for (ordo) or natural order (ordo naturalis) coralline algae. We know of three authors instead of family, are treated as having been 250 P.C. Silva and H. W. Johansen published as names of families." In deciding extended the hierarchy downward, whether a name published with the designa- recognizing two tribes (Melobesieae tion ordo should be considered ordinal or and Coraltineae). Agardh's listing of familial, one must study the entire hierarchi- included genera directly under cal classification to ascertain the author's "orders" in several instances and his intentions, peruse the text in a search for frequent reference to his "orders" as clues, and take into account the historical "families" (e.g. Agardh, 1852, p. 579) context of the work. The three pertinent indicate clearly that his "series" (the cases follow: English equivalent of the German (1) Ordre... Corallineae (Lamouroux, Reihe, a term mentioned in Art. 17.2) 1816, p. 244; 1821, p. 20). Lamouroux is to be considered an order, his had previously (1812) established the "subseries" a suborder, his "ordo" a family Corallineae with approximately family, and that his "tribus" is to be the same circumscription. The absence taken at face value. of a category "famille" between "genre" and "ordre" shows clearly DIAGNOSIS OF ORDER that in 1816 and 1821 he was changing Corallinales ordo novum the designation of the taxon, but not the concept of its rank. Thalli multiaxiales, formarum variabilium, (2) Order Corallinaceae (Harvey, 1849, praeter apices di- vel polystromatici, contextus thalli plus minusve aequabilis aut zonatus pp. 74, 103; 1853, p. 80). Harvey (hypothallus, perithallus, epithallus); stratum usually, but not invariably, applied cellularum meristematicarum plerumque inter- the term "order" to the category that calare, epithallum subjectum; trichocyti today we would call "family", thus aliquando adsunt; synapses primarii obturamenta following a practice entrenched in cum exterioribus stratiis capitularibus tholiformi- bus continentes; parietes cellularum vegetati- mid-19th century literature under the varum plurimarum cum carbonato calcia strong influence of John Lindley. For ("calcite") impraegnati, aliquot genera cum five of the seven "orders" of red algae articulis haud calcificatis. recognized by Harvey in 1849, Structurae reproductivae in conceptaculis included genera were listed directly, portatae; conceptacula asexualia cure uno aut multis poris, tetrasporangia vel infrequenter without intervention of an inter- bisporangia efferentia, tetrasporangiis plerumque mediate taxon. For Corallinaceae, zonatim simultane raro cruciatim divisis; however, Harvey recognized three conceptacula masculina uniporata, fasciculos "suborders" (Corallineae, Nulli- spermatangiorum efferentia; conceptacula poreae, and ? Lithocysteae), which feminina uniporata, filamenta carpogonialia bi- cellulata, unus ad tres a omni cellula supportanta should be considered subfamilies. stratae basalis fertilis producta, saepe peripheriam (3) Ordo ... Coraltineae (Areschoug, versus eonceptacula abortata; nuclei zygotae vel 1852, p. 506). Although in earlier derivativi eorundem ad cellulis supportantis publications Areschoug used the term conjunctionis directis vel indirectis translati; "family", in his monograph of the cellulae supportantes cellulam fusionem ex qua emergunt gonimoblastos efficientes. Corallinaceae he followed the format established by J. Agardh in his Species CoralUnales new order genera et ordines algarum, of which the Thalli multiaxial, of various form, di- or monograph forms a part. The polystromatic except at the apices, with more or hierarchy established by Agardh less uniform or layered tissue structure (1851) in the first part of the (hypothallus, perithallus, epithallus); Florideae, insofar as the coralline meristematic cell layer usually intercalary, lying under the epithallus; trichocytes occasionally algae are concerned, is series Desmio- present; primary pit plugs containing an external, spermeae, subseries Hormospermeae, dome-shaped cap layer; the walls of most and ordo Corallineae. Areschoug vegetative cells impregnated with calcium Reappraisal of the order Corallinales 251 carbonate (calcite); uncalcified joints present in add to the thickness of crusts and some genera. intergenicula, and function at branch Reproductive structures produced in con- apices and crust margins in the ceptacles; asexual conceptacles with one to many pores, producing tetrasporangia or infrequently Amphiroideae and Lithophylloideae. bisporangia; tetrasporangia resulting usua!ly from (3) Plugs of primary pit-connections have simultaneous zonate division, rarely from cruciate two-layered dome-shaped caps in division; male conceptacles with one pore, contrast to capless plugs in the containing groups of spermatangia; female con- Cryptonemiales s. str. Although only a ceptacles with one pore, the carpogonial branches two-celled, with one to three borne on each few species of coralline algae have supporting cell of the basal fertile layer, those been examined (Pueschel & Cole, near the periphery of the conceptacle often 1982), we believe that the sample has a aborted; zygote nucleus or its derivatives trans- taxonomic base sufficiently broad to ported to the supporting cell by direct or indirect give high hope for the usefulness of connection; supporting cell giving rise to a ,u ..... cell from which gonimoblasts are produced. this character. (4) Reproductive structures are produced in roofed conceptacles in all genera DISCUSSION except SporoIithon. The conceptacles Johansen (1981), in his comprehensive of Corallinaceae exhibit more than review of coralline algae, emphasized that one developmental pattern and although these plants exhibit a broad mature structure, but nonetheless are spectrum of growth forms, they are funda- unique. Hildenbrandia also has con- mentally homogeneous. During the past 15 ceptacles, but these are very different years there has arisen an active group of in both development and mature form corallinologists whose voluminous work (Pueschel, 1982). In Sporolithon, tetra- strengthens this conclusion. Genera that sporangia are borne individually in have been given special attention include chambers, small groups of which are Metamastophora (Woelkerling, 1980a, b), homologous to typical corallinacean Mastophora and Lithoporella (Turner & conceptacles. Woelkerling, 1982a, b), Lithophyllum (5) Tetrasporocytes usually undergo (Woelkerling, 1983a), Lithothamnium simultaneous zonate division. In all (Woelkerling, 1983b), Fosliella and other red algae with zonately arranged Pneophyllum (Chamberlain, 1983). We tetraspores, division is successive. believe that the following suite of characters Sporolithon is the only genus of is of ordinal value: corallines in which cruciately arranged (1) Walls of most vegetative cells are tetraspores have been observed, but impregnated with calcite. This form of zonate tetraspores have also been calcium carbonate is also found in reported (Cabioch, 1972, p. 218; Adey, some blue-green algae, charophytes, Townsend, & Boykins, 1982, p. 47). and coccolithophorids, whereas Whether this zonate arrangement aragonite is found in calcareous green results from irregular cruciate algae, brown algae (Padina), and other divisions or from simultaneous zonate red algae (e.g. Actinotrichia, cleavage has not been determined. Galaxaura, Liagora, Peyssonnelia) (see (6) Post-fertilization events involve a Lewin, 1962). cluster of procarpial filament systems. (2) In addition to terminal (superficial, The resulting carposporophyte was marginal) meristems characteristic of termed a "Syncarpium" by Schmitz other red algae, intercalary meristems (1892), implying a compound nature, are common. Dividing cells are by which he meant the involvement of covered by a layer of non-dividing cells numerous auxiliary cells rather than (epithallium). Intercalary meristems multiple fertilizations. (Whether more 252 P. C. Silva and H.W. Johansen

than one fertilization is effected in importance at the ordinal level could be each conceptacle is not known.) The listed, including the consistently two-celled zygotic nucleus, or its derivatives, is carpogonial filaments, the prevalence of conveyed to the supporting cell of the secondary lateral anastomoses, the frequent fertilized filament by either a direct or occurrence of a self-perpetuating, an indirect connection. In general, the presumably diploid, bisporangial phase, and diploid nuclei are thought to move the prominent cell subtending the bi- or through a canal created by partial tetrasporangium. These characters occur fusion of the carpogonium, hypo- individually in other orders, but in combina~ gynous cell, and supporting cell. tion they are unique to the corallines. Delicate transfer tubes have been Two questions suggest themselves. First, reported for a few species, but their where would we place the Corallinales existence has been questioned phylogenetically in relation to other (Woelkerling, 1980a, p. 222; Johansen, floridean orders? Second, if corallines are 1981, p. 102). A fusion cell is considered to represent an order, is there apparently lacking in a few species of justification for elevating the various sub- , but in most genera of families of Corallinaceae to the rank of that subfamily there is reported to be family, and so on down the line? To the first a discontinuous, irregularly shaped question we plead poverty of pertinent fusion cell or several small, poorly information and respiration. The corallines defined fusion cells in each carpo- are highly specialized and might well be sporangial conceptacle (Johansen, placed just before the Ceramiales with 1981). In most genera of regard to their state of advancement, but it Corallinoideae, Amphiroideae, Masto- seems pointless at this time to pursue phoroideae, and Lithophylloideae conjecture concerning their origin. To the a single relatively coherent second question we suggest that hierarchical fusion cell covers nearly the entire inflation should be exercised with caution. fertile area of the conceptacle. Usually We do not perceive an urgent need to only supporting cells participate in fractionate the family at this time. Although the fusion cell, but in two genera tetrasporangial sori (or unisporangial con- there are reports of cells below the ceptacles, as they may be interpreted) and supporting cells also being incor- cruciately divided tetrasporangia set porated (Suneson, 1937; Lebednik, Sporolithon apart from all other corallines, 1977). Gonimoblast filaments grow Adey et al. (1982) believe that this genus is out from the margin or from the lower closely related to Lithothamnium. surface just behind the margin, or from the margin and upper surface of the fusion cell. Usually they do not ACKNOWLEDGEMENTS fuse with other cells, but in three We have been encouraged to prepare this paper genera they have been shown to and have been offered numerous constructive establish open connections with peri- criticisms by several colleagues, especiallyYvonne pheral supporting cells as they grow M. Chamberlain, Kathleen M. Cole, Linda M. Irvine, Curt M. Pueschel, and William radially from small central fusion cells J. Woelkerling. For this support we are grateful. (Lebednik, 1977). We interpret these Richard L. Moe kindly translated the diagnosis peripheral supporting cells as nutritive into Latin. auxiliary cells, homologous to those supporting cells that receive diploid REFERENCES nuclei from the carpogonium and ADEY, W. H., TOWNSEND, R. A. & BOYKINS, W. T. differing from them mainly in time of (1982). The crustose coralline algae (Rhodophyta: Corallinaceae) of the Hawaiian participation. Islands. Smithson. Contrib. mar. Sci., 15: Several characters of secondary iv + 74 pp. Reappraisal of the order Corallinales 253

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