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Home , Marchantiales, Preissia, Riccia

Journ. Hattori Bot. Lab. No. 71: 267-287 (Jan. 1992)

STUDIES ON , I-III

1 R. M. SCHUSTER

I. THE CLASS I FI CATION OF THE G E NUS L. Riccia remains a puzzling group whose intrageneric classification is still unresolv­ ed. Recent chromosome counts (Jovet-Ast 1975; Na-Thalang 1980; Bornefeld 1984) show that in various taxa these range from n = 8, 9, 10 and 12 to n = 16 to n = 24 and 48, with R. caroliniana Na-Thalang, the type of subg. Viridisquamata (Na-Thalang) Jovet-Ast deviant in having n = JO. Subg. Riccia (sect. Riccia sensu Volk & Bornefeld) has chromosome numbers of n = 8, 16, 24 recurring repeatedly, with one [ undescribed] species aneuploid with n = 15, except for R. albosquamata S. Arn., with n = 12. Aside from in the isolated taxa, R. caroliniana and R . albosquamata , thus, chromosome numbers seem to offer little hope for working out an intrageneric phylogeny today. Several taxa (i.a., R. lamellosa s. amplo) occur as polyploid races. If far-reaching attempts at homologizing the basic chromosome complement found in Riccia represent reality, then, eventually, perhaps chromosome structure may give us some aid in refining our classification. To date, it does not. (The attempt by Bornefeld ( 1984) to derive the Riccia genotype, together with that of Takakia and the Antherocotae, from one basic type seems forced to me. We are still not certain if the basic number is 4 or 5 (both are found in Takakia, although Bornefeld states "nur 4 Chromosomen" are found in Takakia; the latter number occurs in anthocerotes). If hepatics and antho­ cerotes belong to different phyla (Schuster 1977), then attempts at drawing homologies based on their genotypes seem pointless to me. In many respects Riccia, and pre­ sumably its genotype, are highly derivative.] Although it has been traditional to accept two subgenera (as, e.g., in Muller 1951 - 58, Hassel 1963, Grolle 1976, pp. 248- 49, Volk 1983), Jovet-Ast (1975, 1984) recog­ nized Thallocarpus and Viridisquamata as additional subgenera. Pteroriccia and Leptoriccia , in addition, were segregated (Schuster 1984, 1985), the first initially at the generic rank but later (Schuster 1985) at the subgeneric rank. Volk and Perold (1986) recently described a monotypic southern African subgenus, Chartacea (with only R. schelpei Volk & Perold). They also recognize a subgenus Spongodes sect. Micantes (Volk & Perold 1986a), with R. hirsuta Volk & Perold as type. This is here regarded as forming an autonomous subgenus. Thus, at the moment, eight subgenera are recognized. I would add here that I am in agreement with Jovet-Ast in recognizing Tha/locarpus ; indeed, in the first stage of MS for Vol. VI of my Hepaticae and

1 Cryptogamic Laboratory, Hadley, Mass. 01035. The research and publication of this work was supported by a grant ( BSR 8709355) from the National Science Foundation. 268 Journ. Hattori Bot. Lab. No. 71 I 9 9 2

Anthocerotae of North America this group was recognized as a subgenus as early as 1953. Volk ( 1983) has drawn a sharp distinction between the two "general" groups currently assigned to Riccia. In the more plesiomorphic group [Ricciella (Spongodes of Volk) and allies] the thallus retains distinct pores and air chambers, and, technically, the dorsal thallus surface is formed of chlorophyllose cells which constitute a true epidermal layer. In the more apomorphic group, thallus development ceases when schizogenous air canals are formed, each typically bounded by four cell rows. In this group (subg. Riccia and allies) we deal, basically, with neotenic organisms: sexual maturity is attained at a time prior to the secondary development of a true . Instead, the distalmost cells of the cell filaments constitute a more or less ephemeral layer (persistent in taxa such as R. nigrella) which is chloroplast free, at least at maturity. A true epidermis, bearing pores, thus fails to develop. In an ontogenetic sense, the distinctions between the Ricciella- and the Riccia-type thallus are rather profound. I think that, perhaps after careful developmental studies are instituted, it may prove desirable to go back to recognizing these two units as separate genera (Ricciella, Riccia) - each with several subgenera. I remain convinced that Ricciella , in many ways, is more closely allied to Ricciocarpus than to the apomorphic taxa, with mature thallus development curtailed - taxa which then would be referred to a nar­ rowed Riccia. At our present level of knowledge, an eight-subgenus system has many advantages over the "traditional" two-subgenus system most recently adopted by Volk (1983). The principle advantage lies in the fact if a multiple subgenus system is adopted, then each subgenus can be divided into a series of natural complexes, or sections. Volk ( 1983, p. 454) states there are roughly 200 species in Riccia. Of these, more than 65%, or well over 120 species, belong in subg. Riccia, as here adopted. These 120-odd taxa would all fall into sect. Riccia in the Volk classification, while the relatively few taxa of subg. Riccie/la (Spongodes of Volk, after elimination of Tha/locarpus) - perhaps under 30 known taxa - are divided into two sections (Grolle 1976, p. 248) or three (Volk I.e.). In Grolle ( 1976, p. 249) some 39 species of Riccia are cited for Europe - alphabetically, because no sectional classification exists. Similarly, the 19 species of this subgenus known from South Africa (Arnell 1963) are also left in a single, undigested group. It is my contention that organizing a mass of over 120 species without recognition of subgroups is virtually impossible; if comprehension of the group is to be advanced and if the mass of species is to be "digested," we are then almost forced to adopt some method of internal organization. The following attempt, of necessity, remains largely provisional because I have collected Riccia species chiefly in North America and in Europe. 2 With study of Australian taxa and those from Africa, unquestionably other sections will have to be

2 This classification into sections has been in MS for about a decade; it was tested last in 1980-83 (taxa from Texas) and 1984- 85 (taxa from Portugal and Spain). R. M. SCHUSTER: Studies on Marchantiales, I- Ill 269

recognized.3 However, existing diagnoses of many of the African taxa (as, e.g., in S. Arnell 1963) hardly allow a certain placement of these . It will become necessary for students residing in these regions, who have access to living material, to test the validity of the sections proposed, and to propose new ones where appropriate. In Vol. VI of The Hepaticae and Anthocerotae of North America the American taxa of Riccia are classified into a number of subgenera (for which see Schuster 1985) and sections; keys to these are given there, obviating a need for including them here. Of the sections, several are new. Latin diagnoses and a brief discussion of each are given here, so as to avoid cluttering up a floristic treatment with such diagnoses.

l. Subgenus Ricciella (A. Braun) Reichenb. Synonym. Subg. Spongodes (Nees) Volk, Mitt. Bot. Miinchen 19: 456, Dec. 31 1983. Grolle (1976, p. 248) lectotypified Ricciella with R. fiuitans L. He cites the combination, sub g. Ricciella (A. Br.) Boulay, Muse. France: 164, 198, 1904; this he corrects (Grolle 1983, pp. 406, 426) as follows: subg. Ricciella (A. Br.) Reichenbach, Deutsch. Bot. Herb. (Nomencl.), p. 23, 1841; (Syn. Red.) p. 213, 1841. Volk adopted Spongodes for subg. Ricciella and in Schuster (1985), without independent review, I followed him, although in Schuster ( 1984) Ricciella is recognized as the correct name for this subgenus. With the lectotypification of Ricciella by R. jfuitans, that name, at the subgeneric rank, has clear priority; it has been used by a diversity of authors in a subgeneric sense. Nees ( 1838, pp. 389- 92) gives us the first comprehensive subdivision of Riccia s. amplo, based on earlier observations of Bischoff, recognizing four sections, as follows: Sectio Lichenoides = subg. Riccia in the modern sense " Hemiseuma = Ricciocarpus, in the modern sense 11 Spongodes = subg. Ricciella sect. Spongodes 11 Ricci e 11 a = subg. Riccie/la sect. Ricciel/a Since Ricciella was raised to subgeneric rank by Reichenbach m 1841, it has precedence over subg. Spongodes of Volk ( 1983). Sectio Frostii Schust., sect. n. Thalli valde dimorphi (ef' multo minores quam .'f ), plerumque intensius pigmentosi; cavernulae aeriae angustae et altae, plerumque in primo strato; sporae per superficiem thalli dorsalis liberatae, non areolatae. Type. R. frostii Aust.; perhaps monotypic. Terrestrial plants, the strongly heterothallic (d" smaller, often vi­ naceous); emergent from dorsum of thallus; spores small, 40-65 µ, nonareolate, bearing vermiculate ridges. Hassel ( 1963) and Schuster (1991) give treatments of the

J Na-Thalang ( 1980) recognized informal groups under sect. Riccia ( = subg. Riccia as treated here), e. g., Group Ciliatae (incL subgroups Longiciliata, Crozalsii), Group Squamatae (incL subgroups Macrospora, Limbata, Sorocarpa) and Group Laevigatae. She similarly divided subg. Ricciella into "Group Terrestriae" (incL subgroups Crystallina, Papulosa, Vesiculosa) and "Group Aquaticae­ Terrestriae." Not enough data are presented in her memoir to warrant any attempt to correlate the informal (hence nomenclaturally irrelevant) groupings she used with the classification here proposed. 270 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 species; the "intermediate" nature of the thallus anatomy of this species is well known. Sect. Frostii is similar to sect. Ca vernosae but differs in being unisexual and strongly heterothallic; it also is unique in the peculiar spores that lack areolation. Unlike in the Cavernosae s. str., the thallus is relatively compact (cf. Hassel I.e., fig . 85). Sectio Cavernosae Schust., sect. n. Thalli rosulas aut hemirosulas formantes segmentis plus minusve oblongis et epidermide mox lacunosa. Squamae ventrales hyalinae, obscurae, biseriatae maturitate; sporangia per superficiem thalli dorsalis liberata; nullo modo vel infirme heterothallini. Type. Riccia cavernosa Hoffm. The Cavernosae perhaps should be regarded as identical with N ees's Spongodes, but the latter, with only R. bullosa Link. [lectotype] and R . crysta//ina L. assigned to the section, are an ambiguous group. The Cavernosae are preponderantly monoecious (although dioecious and weakly heterothallic taxa like P. paraguayensis Spr. exist) and all bear distinctly areolate spores, with distinct wing margins, although the areolae in R. cavernosa are imperfect. Sectio Riccie//a (A. Br.) Bisch. Lectotype. R. jiuitans L. Sect. Riccie//a is readily distinguished by the ventrally protuberant and by the single median row of ventral scales. These scales, often vestigial, may remain undivided (R . .fluitans, R. rhenana) or - apparently (the matter demands careful study) - secondarily tear into two (Hassel 1963, p. 260, fig. 86: d). If, however, R. hubeneriana (R. sullivantii Aust. and R. paranaensis Hassel are probably merely subspecies) has 2-ranked ventral scales, then possibly the section should be divided on that basis. Further study is needed.

2. Subgenus Leptoriccia Schust. (Phytologia 56: 72, 1984) The single species assigned here (R. membranacea G. & L.) has a thallus structure even more delicate than that seen in subg. Riccie//a: the very thin thallus commonly has no ventral tissue per se - merely a ventral epidermis (fig. 999: 1-3 in Schuster 1991 ). As in some taxa of Riccie//a the sporangia strongly bulge ventrally and are, eventually, released through rupture of the thallus underside (fig. 999: 2 in Schuster I.e.). The very delicate, prothallus-like thalli approach those of some species of Thallocarpus, e.g., R. (Thallocarpus) leptotha//us; cf. infra. Leptoriccia, however, differs from all taxa of Tha/locarpus in that: (a) spores are spherical, apolar, and separate relatively soon after meiosis; (b) thalli are bisexual, thus never heterothallic; (c) capsules are ventrally protuberant. The spinulose, relatively small spores are quite unlike anything seen in Ricciella; they, however are somewhat reminiscent in sculpture to those seen in some taxa of Thallocarpus. I assume that Leptoriccia and Thallocarpus originated from a common ancestral type which was not similar to Ricci~fla or to any other extant subgenus of Riccia. R. M. SCHUSTER: Studies on Marchantiales, I- III 271

3. Subgenus Thallocarpus (Lindb.) Jovet-Ast The two outstanding features of Thallocarpus are the permanently united spores and the strongly heterothallic thalli. Although ventral tissue may be scanty (e.g., in R. /eptothallus ), it is usually 3- 5 cell strata high (as shown, e.g., in Hasel 1963, for R. curtisii). Unlike in Leptoriccia, in which the minute pores are virtually indistinguish­ able, pores in Thallocarpus may be conspicuous and, with age, the thallus may be cavernose - the pores rupturing. The of the taxa included here remains ambiguous and my approach to species limits remains ambivalent. Three species appear to be distinct in North America, R. curtisii and the two following taxa. The subgenus is much better developed in South Africa where a single species occurs that is best placed into its own section: Riccia subg. Tha/locarpus sect. Chaetoriccia sect. n. Affinis sectioni Thallocarpo speciebus semper coniunctis e quo differt thallo crasso et firmo, superficie dorsali hirsuta ciliis cellularibus; tetradibus sporarum subglobosis, fasciis coniungen­ tibus inter sporas porosis, non laevibus; sporis densissime papillatis, papillis e humili et denso reticule orientibus. Type. Riccia tomenrosa Volk & Perold. Distinct from sect. Thallocarpus in (a) thalli dorsally armed with long free­ standing filaments formed of elongated cells; ( b) ventral scales conspicuous, apices bearing filaments formed of several cells; (c) tetrads only obscurely tetrahedral, very closely armed with papillae. Sectio Thallocarpus (Lindb.) Jovet-Ast In addition to typical R. curtisii (Aust.) T. P. James, in which the blunt tubercles of the spore tetrads arise from a delicate reticulum, two other taxa occur in North America in which the tubercles arise individually, without a connecting reticulum. In R. curtisii the rhizoids are all, or at least very preponderantly, smooth; in the two following species they are in part conspicuously tuberculate: Riccia leptothallus Schust., sp. n. Affinis R. curtisii sporis remantibus in tetradibus. Differ! (a) tuberculis sporarum ad basem in reticule non iunctis; (b) thallis tenuibus, 4.5- 10 plo latioribus quam altioribus, textura ventrali solo al ta 2- 3 cellulis; (c) marginibus segmentorum limitatis per margin em unistratosum la tum 2- 4 cellulis. Type. Florida, L. M. Underwood 1890- 91 (FH). In this species thalli are much as in R. membranacea: thin, often at least 4.5- 8, often 6- 10 X as wide as high, with ventral tissue only 2- 3 cells high; segments are margined by a unistratose border usually 2-4 cells wide. Riccia howei Schust., sp. n. Affinis R. curtisii sporis remantibus in tetradibus, thallo cavernulas aerias habente in Stratis aerias habente in stratis 2- 4 et e textura ventrali distincta exoriente. Differt (a) thallis laxe ramosis, segmentis saepe lingulatis et usque ad 2 cm longa; (b) sporis, praedita extina, spinas aut tubercula conferta habentibus, singulatim orientibus (in reticule non connexis). Type. Tamiami Canal, Collier Co., Florida (RMS 37303). 272 Journ. Hattori Bot. Lab. No. 71 I 9 9 2

In this insufficiently known species thalli are much as in R. curtisii: the ventral tissue is relatively well developed, in several layers, and the air chambers are in 2- 4 strata. Thalli are less closely branched, segments to 2 cm long, usually 2-4 X as wide as high. Unlike in R. curtisii, spore tetrads (100-125 µ in diam.) have the spore exine with relatively crowded spines or tubercles, ea. 5- 7 µ high, which do not arise from a basal reticulum.

4. Subgenus Micantes (Volk & Perold) Schust., Hep. Anthoc. N. Amer. 6 [in press] Basionym. Riccia subg. Spongodes sect. Micantes Volk & Perold, Bothalia 16(2): 187, 1986. Type. R. hirsuta Volk & Perold. Evidently monotypic. Although assigned to subg. Ricciella [Spongodes] by Volk & Perold, R. hirsuta departs so widely from that subgenus that, without doubt, an autonomous subgenus must be established for this . The dorsal epidermis, which bears obscure pores, is densely covered with a furlike vestiture of tapered, ciliiform hairs, up to 5- 7 cells long. The ventral scales are large, unlike any taxon in Ricciella, with their tapered apices variously ciliate or acuminate. Spores, (95) 115- 125( 130) µ in diam., are much larger than in true Ricciella species. In Schuster ( 1991) the point is made that in subg. Ricciella, as in subg. Leptoriccia, spores are typically relatively small, rarely exceeding 55 µ in diam., and are usually formed in large numbers. In subg. Riccia spores are always large, generally 60--150 µ in diam. or even larger. In this respect subg. Micantes approaches, or agrees with, subg. Riccia. It seems likely that subg. Micantes evolved from the more mesomorphic and usually ephemeral Ricciella complex. The large spores and hirsute thalli are both xeromorphic adaptations.

5. Subgenus Riccia Subg. Riccia includes an enormous number of taxa, many of which have "untidy" perimeters. In Schuster ( 1991) an attempt is made to divide the genus into natural sections. There have been several, mostly informal (e.g., see Na-Thalang 1980), attempts to recognize sections here, or at least groups of species. No systematic attempt has been made, and I am certain that no such effort made today, with our limited understanding of the species, would be wholly successful. A comprehensive under­ standing of the subgenus will become possible only when it is subdivided into sections (and, perhaps, subsections). The following is the best that I can do today. Some of these groups are discussed in considerably more detail, when they occur in North America, in Schuster ( 1991): the others are dealt with only peripherally in that work. Latin supporting diagnoses are given here. In the older literature there are several names, used for species groups or sections, e.g., Squamatae, Ciliatae, etc. I have not attempted to refine or redefine these groups, since conceptually they do not correspond with any of the taxa here recognized. Thus Squamatae has been used for taxa with distinct ventral scales; Ciliatae has been used for taxa with marginal cilia. I think it is pointles to try to lectotypify these groups today: they have served a historical purpose, but do not correspond to sections in the modern R. M. SCH USTER: Studies on Marchantiales, I- III 273 sense. The species I have studied (basically, only Holarctic taxa) fall into a minimum of ten sections; I think with study of Australasian and southern African taxa several more sections will need to be established. My intent has been to establish units no larger than 12- 15 species each (e.g., sect. Riccia) but several sections contain solitary species. The sectional boundaries here adopted are regarded as roughly equivalent to those adopted by Buch (1928), Muller (1951 - 58) and Schuster (1974) in Scapania. The relatively well understood taxonomy of that genus reflects the fact that the many taxa were organized into comprehensible sections; the still appalling taxonomy of subg. Riccia reflects the fact that recent workers have not attempted its subdivision into natural subunits. The heterogeneity of the subgenus is evident from the wide range of chromosome numbers: 8, 9, 10, 12, 15, 24, 36, 48 are all reported.

1. Sectio Riccia Type. Riccia glauca. Species of this section are relatively plesiomorphic . They have thalli naked or bear only short (under 300µ) cilia; they have blunt or even rounded thallus margins; they lack specialized oil-cells; they have relatively small, usually colorless or even vestigial ventral scales which fail to attain the thallus margins; the epithelial cells are unspeci­ alized. All taxa have a relatively weakly impressed antical sulcus which soon broadens and, typically, is swiftly evanescent posteriorly. The section includes a wide array of North American taxa, or taxa that occur in North America (R. glauca, R. tenella, R. bifurca, R. warnstorfii, R. hirta, R. beyrich­ iana, R . ca/ifornica, R. ozarkiana and R. setigera). Only the last is apparently new: Riccia setigera Schust. Differt a aliis taxis sectionis Ricciae plurimis ciliis rigidis et dorsalibus et lateralibus; ciliae 100-150µ longae, sporae areolas 6- 8 trans superficiem habentes; superficies interiores sporarum areolatae velut superficies exteriores. Type. Near Durham, Durham Co., North Carolina (Blomquist 41.871) . This species bears similarities to both R. californica (differing in the spores with 10-13 areolae across the outer face, each 6- 10µ in diam.; in the thallus margins tumid and elevated; in the cilia mostly 160-400 µ long) and R. beyrichiana (different in the obscurely sculptured inner spore faces; the spores to 100-125(130) µ in diam.; in the broader dorsal sulcus of thalli).

2. Sectio Albidae Schust., sect. n. Type. R. a/bida Sull.; also here R. crustata Trab. Affinis Ricciae subsectioni Riccia marginibus rotundis thalli. Differt cellulis epithelii persistentibus, inflatis usque ad conoideas, maturitate per CaC03 obtectis; in sporis parietes valde crasso habentibus, extina obscure sculpta. Thallus with dorsal surface calcified, chalk-white. Spores 80-100 µ, devoid of wing margin, outer face obscurely rugose to alveolate, inner faces similarly but even 274 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 less distinctly sculptured. R. albida and its near ally (?synonym) R. crustata approach many taxa of sect. Riccia in the naked thallus with obtuse to rounded margins. The peristent epithelial cells, however, are tumid or sometimes conoidally inflated, rough with secreted CaC03, and the distinct pores open into canals often bounded by 5- 7 cell rows. The group is very distinct from sect. Riccia in the sharply impressed, persistent dorsal sulcus that does not widen posteriorly.

3. Sectio Sorocarpae Schust., sect. n. Plantae rosulantes, thallis plerumque carentibus pigmento anthocyanino; thalli sulco dorsali profunde impresso, marginibus lateralibus acutis; cellulae epidermicae collabentes, sed basibus rigidibus, pachyderrnicis, perdurantibus. Squamae ventrales parvae, plerumque incolores vel castaneae. Monoeciae. Type. R. soroearpa Bisch. Including besides the type species, R. dorsiverrucosa Hassel and (?) R. mauryana Howe. The group approaches the next (Lamellosae) in the sharply impressed dorsal furrow, which does not conspicuously broaden posteriorly; it also agrees in Jacking cilia and in having distinct, 2-ranked ventral scales. However, the Sorocarpae are distinct in the epithelial cells which have thickened bases, and the ± firm-walled hypodermal cells. Riccia sorocarpa Besides the ubiquitous "typical" R. sorocarpa (subsp. sorocarpa), there are arctic phases (subsp. arctica) and a southwestern form (subsp. erythrophora) dealt with at some length in Schuster ( 1991). Brief Latin diagnoses follow: R. sorocarpa subsp. arctica Schust. subsp. n. Affinis subspeci sorocarpae ( cf. ut super) (a) nullo pi gm en to anthocyanino in marginibus et lateribus et squamis ventralibus thalli; (b) segmentis thalli semper quidem 1.8 plo latiores quam altiores. Differt (a) sporae magnitudine mediana minores (57- 62)63- 83(86- 91)µ diam.; (b) areolae ( 4.8)5- 8( 10) µ diam. ; (c) margine non alato aut ala vestigiali et interrupta. Type. Kangerdlugssuak, Inglefield Bay, NW. Greenland (RMS 45831) . R. sorocarpa subsp. erythrophora Schust., subsp. n. Differt a subspecie sorocarpa et arctica (a) squamis ventralibus vinaceis usque ad purpureas; (b) latitudine segmentorum in thallo aequante 0.9- 1.5 altitudinem, sulco dorsali acutiore et persistentiore; (c) cellulis epidermalibus numquam rostratis, ovoideis usque ad rotundo­ cylindricas; (d) basibus cellularum epidermalium et hypodermalium parietes aut infirme crassos aut nullo modo crassos habentibus. Type. California: 1.5 km W. of Potrero, San Diego Co. (RMS 82-146). This subspecies has an ecology very different from that of the preceding two subspecies: plants are seemingly short-lived and form small hemirosettes. The ventral scales are vinaceous or purple; thallus segments are only 0.9- 1.5 X as broad as high; epidermal cells are never beaked and are ovoid or rounded-cylindrical.

4. Sectio Lamellosae Schust., sect. n. Plantae monoeciae, numquam ciliis in marginibus aut in superficiebus; thalli sulco mediano, acuto, perdurante, profunde impresso atque marginibus lateralibus acutis usque ad sublamellatos; R. M. SCHUSTER: Studies on Marchantiales, 1- 111 275 sporae aerolatae, brunneae et translucentes, margine alato angustissimo aut absente. Type. R. /amellosa Raddi. The Lamellosae are one of the very large and difficult sections of subg. Riccia. At least 7 species occur in North America (R. lamellosa, R. andina s. amplo, R. macal­ listeri, R. dictyospora, R. nigrella, R. campbelliana, R. albolimbata); a considerable number of other species occur in southern Africa, which may be the center of diversity. Unlike the allied Sorocarpae, in which spores usually show at least a weakly tetrahedral form and a slight wing margin, the bulk of taxa fitting here have apolar spores, or almost apolar spores, with the wing margin vestigial or lacking; spores are usually spherical or nearly so. This is not so in some species (R. nigrella, R. campbelliana) but tendencies for Joss of the wing margin are a significant phylogenetic tendency in this group. The taxonomy of this group remains impenetrable. Most taxa are very variable, especially R. lamel/osa s. amplo. The following two taxa from the Americas appear distinct: Riccia campbelliana subsp. austrigena Schust., subsp. n. Differt a subspecie campbelliana (a) sporis maioribus 100-120 µ diametro; (b) squamis ventralibus violaceis usque ad purpureas, incoloribus solo in marginibus; (c) segmentis thalli acutis sed numquam sublamellatis. Type. Argentina: Dept. Tafi, La Cienga, Tucurnan (Sleumer 1755) . It is likely that this plant, when better known, will need to be given autonomous species rank. In no North American phase of R. campbelliana, even from exceedingly exposed loci, are ventral scales ever purplish-pigmented. Riccia andina subsp. chionophora Schust., subsp. n. Differt a subspecie andina squamis maximis ventralibus hyalinisque; thalli plerumque (2)3- 4 plo dichotomi, sed segmenta solo l.0-1.5(2) mm lata, ut maximum l.5- 2 plo latiora quam altiora. Type. Emory Peak, Big Bend Natl. Park, Texas (RMS 81-1241) . R. andina K. Muller, described from Argentina, is not known with spores. It appears to be an alpine derivative of R. lamellosa. The above plant, known with spores, has a spore ornamentation quite different from that of R. lamellosa. The subsp. chionophora was given its name because, dry, it is snow-white: the large, ventral scales, undulate, become quite conspicuous when plants are dry and thallus margins are incuved or connivent. The very large ventral scales easily separate it from subsp. andina. When better known these two taxa may have to be treated as autonomous species.

5. Sectio Albosquamatae Schust., sect. n. Thalli inermes cillis aut papillis; latera verticalia aut subverticalia; margines tenues, ascen­ dentes, lamellati (in sectione transversa non profunde lunati e visu dorsali); superficies dorsalis ± nitidida; cellulae epidermicae parietibus tenuibus, ephemerae, subcubica (visa in sectione transversa thalli). Squamae ventrales margines thalli valde excedentes, imbricatae, semilunatae, omnino marginatae, incoloratae basibus plus minusve purpureis exceptis; cellulae aliquando in 276 Journ. Hattori Bot. Lab. No. 71 1 9 9 2 stratis ordinatis, brevi-oblongae, magnae (ea. 50-70 µ) parietibus crassis. Type. R. albosquamata S. Arn. (Mitt. Bot. Staatssaml. Miinchen, Heft 16: 266, fig 1, 1957). The ventral scales, with regularly oriented, almost quadrate, very firm-walled cells, are apparently unique. Bornefeld ( 1984) reports that the haploid chromosome number of this species is 12 - a unique number in Marchantiales; it is not reported for any other Riccia .

6. Sectio Atromarginatae Schust., sect. n. Affinis sectioni Ricciae thallo in sectione transversa (sulco dorsali non profundo, Jato facto et evanescente, et marginibus thalli obtusis usque ad subacutos) et squamis ventralibus minimis. Differt (a) sporis sine margine distincta alata, paene apolaribus, areolas minutas habentibus; (b) intense venetis et lateribus subatris; (c) ciliis brevibus et papillis clavatis in lateribus et superficie thalli plerumque factis. Type. R. atromarginala Lev. ex Martelli; also here R. violacea Howe and R. iodocheila Howe. TheAtromarginatae are only obscurely allied with the sect. Riccia (with which are shared proclivities for forming short cilia of thallus margins and sometimes dorsal surfaces) and with sect. Lamel/osae (with which are shared the tendency for a rather sharp, if short, antical median sulcus of the thallus). Distinctive for the group is the tendency for development of both blunt papillae (sometimes purplish-pigmented) + hyaline, sharp, rigid cilia. The thalli are a dull bluish green dorsally and deep purplish or black-purple laterally. Spores are distinct in their opacity at maturity; the very small areolae or alveoli; and their nonpolar nature; wing margins are lacking or virtually so.

7. Sectio Ci/iiferae Schust., sect. n. Plantae valde xeromorphae, squamis ventralibus incoloribus et magnicellularibus (ea. 35- 60 X70-120µ); apices segmentorum tuberiferi, margines lamellati, tenues sulco mediano acute impresso in apicibus; margines thalli (et aliquando superficies) ciliati; dioecii. Type. R. ciliifera Link ex Lindenb. R. donnellii is regarded as identical with R. gougetiana. As far as known, plants are unisexual - a rare feature in subg. Riccia; the plants are long-lived perennials, typically dying back to the tuberous apex of the thallus. The tubers may be cylindrical and geotropic. In no other North American complex do thalli develop apical tubers.

8. Sectio Ciliatae Schust., sect. n. Plantae dense ciliatae, ciliis lucentibus et longis (usque ad 1100 µ) et saepe arcuatts m marginibus et lateribus; segmenta obtusa usque ad lateraliter rotunda, sulco dorsali plus minusve distaliter acuto, mox evanescente; cellulae epidermicae mox collabentes, membrano tenui; monoeciae; sporae opacae et nigrae. Type. R. ci/iata Hoffm. R. trichocarpa and R. canescens are regarded as merely subspecies of R. ciliata , specialized for survival under exceedingly difficult conditions. A fourth subspecies is as follows: Riccia ciliata subsp. grisea Schust., subsp. n. Differt aliis subspeciebus R. ciliatae setis valde conspicuis, nitidis, tenuibus, saepe curvatis, R. M. SCHUSTE R: Studies on Marchantiales, I- III 277 usque ad 750-900( 1100) µ longas et lateribus ± concoloribus; plantae siccae subgriseae. Type. Near Bastrop, Texas (RMS 82-320) . This plant, widespread on the Edwards Plateau, and somewhat to its east and west, has much longer cilia than subsp. trichocarpa. It appears allied most closely to subsp. canescens. The problematic taxonomy of these largely geographically segregated races of the protean R. cilia ta are dealt with in detail in Schuster (1991).

9. Sectio Sommieri Schust., sect. n. Affinis Sorocarpis sectioni cellulis hypodermalibus parietes crassos habentibus. Differt (a) cellulis epidermalibus sphaericis et parietes tenues ubique habentibus; (b) squamis ventralibus atro-purpureis et magnis; (c) lateribus thalli atro-purpureis, velut alae angustae laterales factis; (d) latera infra margines paene verticalia; (e) textura ventrali magna aequante 0.6--0.65 altit­ udinem thalli. Type. R. sommieri Levier in Sommier. Thalli thick (wings aside, cross sections almost as high as wide), with vertical flanks and sharp, lamellate margins; epidermal cells delicate, the hypodermal strikingly thickened. Spores areolate, 70-80 µ. Apparently monotypic. The differentiated hypodermal cells suggest R. sorocarpa and R. dorsiverrucosa.

10. Sectio Bicarinatae Schust., sect. n. A omnibus aliis sectionibus differt thallo obtuso et ciliis saepius formatis, ciliis peculiaribus et valde acutis et subtiliter papillosis et parietem crassam habentibus et ciliis basaliter aggregatis binis ternisve. Segmenta ut in sect. Riccia, marginibus obtusis et sulco dorsali mox Jato convexoque (sic in sectione transversa duo sulci non profundi et proximi sed iuga convexa separati). Type. R. bicarinata Lindb. Thalli with semicircular to lunate cross section, the ascending flanks blunt on their margins; dorsal surface with sulcus soon widening, forming 2 shallowly impressed lines. Thallus margins with groups of 2- 3 basally connate, thick-walled, sharp cilia. Without any close ally; the marginal armature is unique.

II. THE INTRAGENERIC CLASSIFICATION OF MANN/A 0PIZ In a list of European Hepaticae Grolle ( 1983, p. 405) divided into two subgenera, Mannia [type: M. triandra (Scop.) Grolle = M. raddi Opiz] and Xerom­ annia Grolle, the latter divided into two sections, each monotypic: sect. Xeromannia [with M. androgyna (L.) Evs.] and Sindonisce (Corda) Grolle [with M. fragrans (Balb.) Frye & Clark]. Xeromannia supposedly differs from Mannia s. str. in the "robust" size and the compact assimilatory tissue, the air chambers divided by many septa and walls. One additional criterion is cited: that the thallus is scarcely areolate dorsally. Several comments on this proposed subdivision are needed: ( 1) the malleability in degree to which the aerenchyma tissue is subdivided in the M. pilosa-sibirica complex is so great (Schuster 1953; see, in particular, pl. 80 and appended discussion) that there 278 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 is no way in which Mannia can be divided into two subgenera - or even sections - on the bases outlined by Grolle. Being thoroughly familiar with M. androgyna and M. fragrans in the field, I also see no point in two monotypic sections. Both of these taxa admittedly have the thallus dorsally scarcely areolate (a supposed subgenerc criterion of Xeromannia) - but this is exactly the case in M. pilosa and M. sibirica, which Grolle leaves in subg. Mannia. In the degree to which the assimilatory tissues are subdivided, indeed, M. sibirica and M. fragrans are essentially identical. Xeromannia supposedly differs from Mannia in the "frons robusta." However, M. androgyna, the type of Xeromannia, is essentially identical in size to M. pilosa and M. sibirica - and is considerably smaller than M. fragrans. M. californica is also transitional in size. Indeed, on the basis of vigor, degree of subdivision of the aerenchyma tissue, and all other criteria, the species of Mannia form a continuum that makes adoption of subgeneric and sectional criteria futile. If any intrageneric division is to be adopted, perhaps one can be devised on more fundamental criteria, rather than the superficial ones employed by Grolle. The most fundamental feature, in my opinion, is the form of the if' receptacle and its position. In M. pilosa and M. sibirica the circular androecia are sharply defined and usually terminate stipitate-based ventrolateral segments of limited size and determinate length ( cf. Muller 1951 - 58, fig . 65 : f- h; Schuster 1953, pls. 78: 6, 79 : 1). However, even here if' discs may arise from apical innovations (pl. 79 : I in Schuster 1953). By contrast, in M. triandra Muller describes the androecia as in the form of small cakelike discs at the thallus apices; similar disciform androecia dorsal on the main thallus are well known in M. androgyna (and are shown in the old, much-copied figure of Bischoff 1835), in M. californica, and in M. fragrans (cf. the old figure of Bischoff 1835, copied as fig . 59: 3 in Muller 1951 - 58). Even here there is considerable variation and androecia, even though dorsal on leading thallus segments, may be reduced to a few scattered antheridia not forming defined discs ( cf. pl. 78: I in Schuster 1953). Similar variation from tumid and "condensed" androecia to scattered antheridia dorsal on the thallus occurs in M. californica. As a consequence, I fail to see much point in adopting the superficial subgeneric division proposed by Grolle and the name Xeromannia is best suppressed. In turn, the two monotypic sections recognized under subg. Xeromannia are equally useless: the two species are clearly rather closely allied. It should be noted that Grolle ( 1976, pp. 245- 46) had earlier proposed a similar classification, but wholly different nomenclaturally. He adopted Mannia subg. Mannia, with: SectioMannia [typecited: M. androgyna (L.) Evs. = M. dichotomasensu Raddi] . Supposedly also including M. capensis (Steph.) S. Arn. and M. californica (Gott.) Wheeler. The latter is so close to M. fragrans that sterile plants at times can hardly be separated from M. fragrans. Sectio Sindonisce (Corda) Grolle (type : M. fragrans). Mannia subg. Arnelliella (Mass. ) Grolle (type : M. sibirica) . The virtues (or lack thereof) of this arrangement are exactly those of the I 983 divisions adopted, hence need no separate comment. Utilizing the thallus criteria R. M. SCHUSTE R: Studies on Marchantiales, I- III 279

Grolle would use for his classification, the following progression from a "compact" to a "loose" thallus structure is recognizable:

I. M. ca/ifornica } subg. Xeromannia Grolle ( 1983) = subg. Mannia (Grolle 1976) 2. M. fragrans 3. M. sibirica 4. M. pilosa subg. Mannia Grolle ( 1983) = subg. Arne/lie/la (Mass.) Grolle ( 1976) 5. M. triandra } Of these taxa, 3- 4 form a transition in thallus structure (compare pls. 79: 4 and 80: 1- 2 in Schuster 1953), yet M. sibirica may have a thallus anatomy falling close to 2 (compare pl. 80: 4- 7 with 80: 10--11 in Schuster Le.) . The 1976 classification by Grolle is particularly unnatural if we contrast M. californica and M. fragrans. I have noted the very close similarity of these two taxa, as regards the vegetative thallus and its anatomy. The two taxa, furthermore, show two very significant phylogenetically relevant "tendencies": ( 1) Both show variation from one population to the next in the degree to which androecia are differentiated. In both androecia may be somewhat elevated as ill-demarcated "cushions," but in both and­ roecia per se may be lacking: isolated antheridial ostioles, varying in numbers, may occur dorsal on the thallus. In either case, androecia are always dorsal on a leading thallus segment and never occupy reduced, stipitate, lateroventral innovational bran­ ches. (2) In M. fragrans there is a tendency for the formation of -'f receptacles at apices of branches that show varying degrees of reduction; these branches may arise from the costa of leading androecial thalli. However, -'f receptacles often form at apices of long, or leading, thalli - but never, in my experience, on thalli that had first produced androecia. In this malleability in form and position of -'f receptacular segments M. fragrans is clearly plesiomorphic vis a vis M. californica. The latter has "fixed" the tendency already seen in M. fragrans for abbreviation of -'f branches: the leading (eventually always androecial) thallus in M. californica bears several latero­ ventral, intercalary branches that soon form -'f receptacles. Indeed, thalli may be pinnulate with such reduced -'f branches - even more freely so than shown in Schuster (1991 ). M. fragrans and M. californica are thus very closely allied and clearly must be retained in a single section. In Feb.-March 1991 I made numerous mass collections in the Santa Rita and Santa Catalina Mts., in southern Arizona. The above generaliza­ tions are based on study of literally hundreds of thalli of these two taxa. Thus placing them into two sections (Mannia, Sindonisce) as in Grolle ( 1976) is quite untenable. Furthermore, M. androgyna, of which hundreds of plants were studied (near Almufi­ ecar, Spain, 1985) is, in my opinion, very close to those two species in the androecia: these are dorsal on leading thalli, at best weakly defined as slightly tumid "cushions," but sometimes no more sharply circumscribed than in M. fragrans and M. californica. However, we wish to "order" the taxa of Mannia, it is my contention that these three species must remain in one section. 280 Journ. Hattori Bot. Lab. No. 71 1 9 9 2

III. ON QUADRATA (SCOP.) NEES, P. MEXICANA STEPH. AND CHENOPODA L. The genera Preissia and Marchantia are uniformly accepted as distinct from each other. Evans (1923, pp. 57, 61, 62) separates them as follows:

Preissia Marchantia I. Apical innovations (beyond the ~ receptacle) Apical innovations lacking present 2. Cupules (bearing discoid gemmae) lacking Cupules (bearing discoid gemmae) present 3. ~ Receptacles with stalk destitute of green ~ Receptacles with stalk bearing 1 or 2 bands tissue of green tissue bearing pores and air chambers 4. Ventral scales in 2 rows Ventral scales in 4 or more longitudinal rows 5. ~ Receptacle slightly lobed, normally 4- ~ Receptacle with "mostly 5- 9" rays rayed The last distinction, given in contracted form here, represents a simplification of a much more complex situation. In Preissia the virtually unlobed carpocephalum normally bears 4 dorsal ridges, corresponding to the "rays" in Marchantia. In both the archegonial groups supposedly lie alternate with (thus between) the rays. Schiffner (1893, pp. 279-284) carefully dealt with the morphology of the carpocephala in Marchantia vis a vis those of Preissia ("Chomocarpon"). He already had pointed out that in both the genus Preissia, and in Marchantia chenopoda (and M. geminata), there are always only 4 perichaetia ("gemeinsame Htillen") vs. the "normal" initiation of ea. 8 archegonial groups, each enveloped by a perichaetium, in Marchantia s. str., e.g., M. polymorpha et al. In the latter the carpocephalum is normally formed of a 3-fold dichotomy ("dreimalige Gabelteilung"), so that 8 growing points occur on the devel­ oping carpocephalum - from each of which an archegonial group is developed. This is shown schematically in Muller (1951-58, fig. 19: p-q, p. 82). By contrast, in Preissia (and in M. geminata) only a 2-fold dichotomy characterizes the carpocephalum: hence only 4 archegonial groups, each surrounded by a perichaetium, are found. Schiffner (I. c., p. 280) makes the point that M. geminata (the type of Marchantia subg. Proto­ marchantia Schust.; cf. Schuster 1985) breaches the chief distinguishing feature ("hauptsiichlichstes Unterscheidungsmerkmal") that has previously always been cited as the most important one separating Marchantia and Preissia. The distinction of the two genera would not need to be reexamined were it not for the case of Preissia mexicana Steph. This species was already placed as a synonym of M. chenopoda by Evans ( 1923, p. 65) and he stated that Preissia s. str. [e.g., P. quadrata (Scop.) Nees, the only taxon generally recognized in Preissia] occurred from "Arctic America ... as far south as Virginia and Colorado." There is, however, a collection from Mexico, determined by R. Svihla as P. quadrata, collected in Mexico, from Hidalgo: ea. 5 km S. of Chapuljuacan (Frye & Frye 2846). Two packets of this number have been examined. Their study has clarified both the status of P. mexicana and the actual southward range of P. quadrata. Their study, furthermore, has raised questions as to the relationships and distinction between Preissia and Marchantia. Indeed, careful R. M. SCHUSTE R: Studies on Marchantiales, I- Ill 281 study has shown that of the 4 criteria enumerated above, l, 3, 4, and 5 fail to clearly distinguish the two genera. This study, in fact, suggests that Preissia and Marchantia are much more closely allied than has been generally recognized. This conclusion - which, initially, I believed to be quite novel - was, in fact, clearly stated long ago by Schiffner (1893, p. 280). I return to this theme later (p. 286) . In addition to the dubious P. mexicana of Stephani (Hedwigia 22: 49, 1893 ), and of the dubious report of P. quadrata from Mexico, two other taxa have been described from Latin America under Preissia : ( 1) From Chile, P. cucullata Nees & Mont. in Montagne, Ann. Sci. Nat., Bot., Ser. 2, 9: 44, 1838; this is identical to cruciata (L.) Dumort. ex Lindb. (2) From Bolivia, P. barbara Herzog, Bibliotheca Bot. 88: 27, 1921; this is M chenopoda. On the following pages it is shown that the report of P. quadrata from Mexico represents a phase of M. chenopoda. Thus not only the Mexican P. mexicana but also the Bolivian P. barbara are identical to M. chenopoda. Why should species of these supposedly widely different genera be repeatedly subject to confusion? In trying to answer this question, one runs into problems whose resolution raises interesting phylogenetic questions. Ultimately it is the general problem of how close - and how distinct - Preissia and Marchantia are that is the subject of this investigation. The following points require elaboration: 1) Preissia and Marchantia chenopoda have a very similar thallus cross section. Muller ( 1951- 58, fig . 84: b) draws the former as with a thin dorsal chlorenchyma layer and a ventral compact tissue with a "band" on each side of the thallus midline of darker tissue; he notes that this tissue is mycorrhizal. He also draws in scattered sclerenchyma fibers. Virtually identical thallus cross sections occur in M. chenopoda (Fig. 2: 2), even though the two mycorrhizal bands may here be confluent along the thallus midline. 2) Ventral scales in Preissia are supposedly 2-ranked (Evans 1923; Muller 1951- 58, p. 385) while in M. chenopoda, besides the 2-ranked conspicuous, appendiculate ventral scales arising immediately adjacent to the ventral thallus midline, there is a lateral row on each side of nonappendiculate scales that are (teste Hassel 1963, p. 177) "mas pequefias, alternado con las medias"; her fig . 65 : j clearly shows some of them. As Fig. 1: 24-25 shows, they are not only smaller but inserted on an asymmetrical, arched line that is much shorter than the corresponding appendiculate scales (compare Fig. I: 16- 17). The appendiculate ventral scales in Preissia and M. chenopoda are basically similar in form: asymmetrically lunate, with a single appendage; the appendage is typically somewhat constricted at its juncture with the scale body. In M. chenopoda it also usually has one or both sides reflexed toward the base (Figs. l: 16-18; 2: 7, 10). In both Preissia and in M. chenopoda the ventral scales and their appendages apparently Jack oil-cells (Muller Le. , p. 387; Hassel I.e., p. 177 mentions 1- 3 cells "con oleocuerpos" at the base of the ventral scales in M. chenopoda; I have not been able to find them). In M. chenopoda, however, the laminar portions of ventral scales may give rise to rhizoids (cf. Fig. 1: 16- 17, 21), and rhizoid-initials may be confused with oil-cells (cf. Fig. 2: 7- 8), although perhaps isolated scales may bear 1- 3 oil-cells. 282 Journ. Hattori Bot. Lab . No. 71 I 9 9 2 R. M. SCHUSTER: Studies on Marchantiales, I- III 283

In both Preissia and M. chenopoda the ventral scale body bears marginal slime papillae (Figs. 1: 6-8; 2: 11 ), although they seem more frequent in the former. In both the appendage is formed of relatively large cells vis a vis peripheral parts of the body of the scale (Figs. 1: 7- 8, 18; 2: 10). In Preissia, however, marginal and intramarginal cells of the body, adjoining the point of origin of the appendage, are not notably smaller celled (Fig. 1: 7- 8) while in M. chenopoda a small-celled field is evident (Figs. 1: 18; 2: 10). The appendage in both taxa tends to develop a few 1- few-celled lateral teeth (Figs. 1: 7- 9, 16- 18; 2: 9- 10), although these teeth may be reduced or lacking (Fig. 1: 23). Hassel (I.e., fig. 65: A-H) shows much the same for Argentine material of M. chenopoda. Although the lateral, nonappendiculate rows of ventral scales in M. chenopoda are clearly evident, rudiments of such scales also occur in Preissia - even though they have been overlooked. When visible, they are basically triangular, relatively few-celled, and armed marginally with conspicuous, clavate slime papillae (Fig. 1: 5). Thus the differences in this regard between Preissia and Marchantia are clearly bridged. Schiffner ( 1893, pl. 19: 18, 19) shows only 2 rows of ventral scales in M. geminata. These, exactly as in Preissia and in M. chenopoda, tend to develop lateral marginal teeth of the appendages and they tend to be constricted at their juncture with the body of the scale. The dubious phylogenetic position of M. geminata has already been noted above. Clearly the number of rows of ventral scales in the Marchantia-Preissia complex seems to be devoid of major significance. 3) In the Mexican material of "Preissia quadrata" (Frye & Frye 2846), here placed in M. chenopoda, a few of the !f- plants examined unmistakably bear apical innovations - much as is typical of Preissia. The criterion, thus, loses much of its relevance. Furthermore, in Marchantia papillata s. !at. the !f- thallus branches may innovate below and distad of the archegoniophores (Schuster 1991, fig. 971: 1, Al). 4) In both Preissia and M. chenopoda the !f- receptacle is very shallowly 4- 5-

FIG. I. Preissia quadrata (1 - 10) and Marchantia chenopoda ("Preissia mexicana" ( 11 - 25). I. Aerenchyma-c hlorenchyma layer, cross section, with pore ( X215) . 2. Pore, external aspect ( x 215 ). 3. Ventral tissue, cross section, showing sclerenchyma cells ( x 215). 4. Ventral scales ( X 16). 5. Accessory ventral scale ( x 215) . 6-10. Portions of ventral scales; fig. 6, apex of body; figs. 7, 8, appendages and adjoining parts of body; fig . 9, appendage; fig. 10, median-basal cells (6- 9, X 85; 10, X 95 ). 11. Cross section of archegoniophore stalk ( X42). 12, 13. Parts of fig. 11 , including the incurved modified thallus margins ( x 96). 14. Part of fig . 11, with air chamber ( X96). 15 . Part ofperichaetium mouth ( X96). 16, 17. Ventral scales, from the two median rows; in fig . 16 some of the rhizoids drawn in; in fig. 17, rhizoid bases indicated only ( X 16) . 18. Apex of ventral scale, with appendage ( x 50) . 19- 22. Parts of ventral scale; fig . 19, apex of appendage; fig . 20, median-basal cells of body; fig . 21, median cells, showing bases of rhi zoids; fig . 22, marginal and distal cells of body ( x 220). 23. Two ventral scale appendages ( X 50). 24, 25. Scales from lateral two rows of ventral scales ( X 16). [ 1- 10, from plants from Conway, Mass., RMS 65-909; 11 - 25, from Mexican plants determined by Svihla as "Preissia quadrata" = "Preissia mexicana" = Marchantia chenopoda ; 1- 3, 5, drawn to 150µ scale; 4, 16, 17, 24, 25, drawn to l.Omm scale; 6-9, drawn to 200 µ scale; 10, drawn to 180 µ scale; 11, drawn to 500 µ scale; 12- 15, drawn to 300 µ scale; 18, 23, drawn to 400 µ scale; 19-22, drawn to 80µ scale.] 284 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 lobed, with 4 archegonial clusters, each surrounded by a perichaetium. Hence, as Schiffner (I.e.) already noted, there is no obvious difference between the two taxa in this regard. As Hassel (I.e., fig. 62 : e) clearly showed, the perichaetia in M. chenopoda alternate with the broad and low "rays" or lobes of the carpocephalum. Milller ( 1905- 16, fig. 183) drew a schematic diagram of the carpocephalum of Preissia : here the 4 archegonial clusters also alternate with the rays (which are elevated as ridges on the upper surface of the carpocephalum), but he noted that there was a tendency for the lobes to grow out, secondarily, between two of the rays (hence distad of each archegonial group). The origin, from successive condensed dichotomies of the car­ pocephalum, remains clear in M. chenopoda (the mature carpocephalum is bilaterally symmetrical), while in Preissia, with greater condensation, the carpocephalum is no longer bilateral and has become radially symmetrical. Despite the wide-ranging similarities between Preissia and M. chenopoda - which Schiffner (I.e.) had already emphasized - vegetative thalli of the two taxa show several clear differences - even when gemma cups are lacking. Among these are: l) In M. chenopoda pores are larger and surrounded - as seen in superficial view - by 3-4 rings each formed of 7- 9 to 8- 12 cells (in the outer 2- 3 rings; Fig. 2: 6). In cross sections the barrel-shaped pore is formed of usually 6 rings of cells (Fig. 2: 3- 4 ). By contrast, in Preissia pores are typically surrounded by 2- 3 rings of cells, each normally formed of (3)4- 5 cells (Fig. 1: 2) . Of more importance, in M. chenopoda the lowermost ring of cells is formed of ( 4) 5- 6 or more cells and these cells fail to project significantly internally, so that the pore is wide open (Fig. 2: 6). However, the innermost (lowermost) ring of cells in Preissia is usually formed by 4 cells which strongly project internally - to the point where a slight, cruciate opening only is left (Fig. l : 2). The difference in the pores, as seen in a vertical section, is significant (compare Figs. l: l and 2: 3- 4). 2) Appendiculate ventral scales in the material of M. chenopoda here studied tend to develop conspicuous laminar rhizoids (Fig. 1: 16- 17, 21) but I have not seen them - or they are, at least, rare and sporadic - in Preissia. In M. chenopoda there is typically a field of rather small cells of the distal part of the lamina of the scale, contrasted to the large-celled appendages (Figs. l: 18; 2: 10); basad of these small cells, the laminar cells are rarely to sporadically sigmoid (Fig. 2: 8, 10; l : 18, 20). By contrast, in Preissia the cells, marginal and intramarginal, below the base of the appendage are not size-differentiated (Fig. l : 7-8) but these, and those basad of them, tend to be irregular and often sigmoidal in form. In the Mexican plants of M. chenopoda ventral scale appendages are always relatively small and few-celled - although never quite as small as in Preissia (compare Fig. 1: 4 and 16-17). By contrast, in more "normal" plants of M chenopoda at least some ventral scales are many-celled and much larger (compare fig. 65 in Hassel 1963). On gynoecial plants of M. chenopoda (and the Mexican plants referred by Svihla to "Preissia quadrata" are .'f. ) another major distinction emerges: the stalk of the carpocephalum bears 2 rows of air chambers of the, technically, dorsal surface (Fig. l: R. M. SCHUSTER: Studies on Marchantiales, I- III 285

FIG. 2. Marchantia chenopoda. I. Pegged rhizoid, cross section ( X 222). 2. Thallus cross section; pigmented band stippled ( X 220). 3. Pore, in vertical section ( X 222). 4. Sector of thallus in cross section, intersecting a pore ( X 222). 5. Cross section of part of ventral tissue, showing a scleroid ( X 222). 6. Epidermal cells with pore; the lowermost ring of bounding cells of the pore stippled ( X222). 7. Ventral scale; rhizoid-initial bases shown ( X 16). 8. Cells from lamina of fig. 7, a rhizoid base drawn in ( X95). 9. Ventral scale appendage ( X41). 10. Ventral scale appendage and adjacent portion of scale body ( X41). 11 . Marginal cells of body of ventral scale, from adjoining area at arrow in fig . 10 ( X 95). (All drawn from plants determined as Preissia quadrata by Svihla, from Mexico. Fig. I: 11 - 25 drawn from same material; I, 3- 6, drawn to 80 µ scale; 2, drawn to I mm scale at left; 7, drawn to I.Omm scale at right; 8, 11 , drawn to 200µ scale; 9, 10, drawn to 400µ scale.

11, 14). These air chambers are rudimentary and form 2 distinct ridges; pores - if present at all - may be difficult to demonstrate and the chlorophyllose filaments are typically only 1- or 2-celled. [By contrast, in more "normal" species of Marchantia, such as M. polymorpha s. /at., a wide band of air chambers covers the entire dorsal surface of the stalk; cf. fig. 46: K in Hassel I.e.] In Preissia the stalk of the carpocephalum is devoid of chlorenchyma and lacks air chambers. Finally, on gynoecial plants the perichaetium at the apex shows the "usual" fringe of cilia (Fig. 1: 15), seen in often even more elaborate form in other Marchantia species (cf., e.g., fig . 48: A, M. polymorpha, in Hassel I.e.). In Preissia, by contrast, the perichaetia are "subentire" at the mouth, as Evans ( 1923, p. 61) noted. Conclusions: ( 1) Mexican material attributed to Preissia quadrata = Marchantia chenopoda. (2) Although Stephani (1899, p. 155, in 1898-1924) placed his Preissia mexicana as a synonym of P. quadrata, it probably is a synonym of M. chenopoda, as 286 Journ. Hattori Bot. Lab. No. 71 I 9 9 2 already noted by Evans (I.e.); in the absence of a type this must remain speculative. (3) M. chenopoda is a highly malleable taxon and requires further study. Thus even though some collections show appendiculate ventral scales whose appendages are bordered by cells that tend to be elongated obliquely (or almost radially) to the appendage margins ( cf. fig. 65: A, C- E, H in Hassel I.e.), some plants - including those from Brazil ( cf. fig. 65: B, Gin Hassel I.e.; and Figs. 1: 18, 23 and 2: 9- 10, from Mexican plants) show appendages whose marginal cells are not differentiated from the intramarginal and are not, or rarely and sporadically, obliquely oriented. ( 4) Plants of the last type, with mostly smaller and fewer-celled appendages of the ventral scales, show an approach, in the cellular details of these appendages, to P. quadrata. Since Schiffner ( 1893, p. 280) had already noted that Marchantia geminata and M. chenopoda have carpocephala with only 4 archegonial "clusters," each enveloped by a common perichaetium ( cf. fig . 62: E in Hassel I.e., as well as pl. 19: 2 in Schiffner I.e.), exactly as in Preissia, the most salient distinguishing feature between Preissia and Marchantia disappears. Indeed, he noted that in thallus structure, form of the pores, and of the c? and ~ receptacles, there is no real difference ("wesentlicher Unter­ schied") between Marchantia and Preissia. He also noted that if M. chenopoda did not develop the characteristic gemma cups of other Marchantia species, one could auto­ matically ("unbedenklich") place this taxon into Preissia. He concludes that it might be more natural to unite Preissia and Marchantia. In view of the difficulties, docum­ ented on the foregoing pages, which workers have had - including Stephani, Herzog and Svihla - in attempting to distinguish M. chenopoda from Preissia, this conclusion of Schiffner's acquires a new dimension. Ultimately, three criteria principally serve to distinguish the two groups: (a) presence of gemma cups in Marchantia, their lack in Preissia; (b) presence of at least rudimentary chlorenchyma and air chambers of the carpocephalum stalk in March­ antia, their lack in Preissia; (c) the fringed and ciliate perichatium mouth of March­ antia vs. the subentire mouth in Preissia.

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