4MORPHOLOGYfilamentous, uniseriate protonema. Cell specializationgree - PDF document

4MORPHOLOGYfilamentous, uniseriate protonema. Cell specializationgreen filaments, the chloronema. Each protonema canfilm over its substrate. Fragments of chloronema, cut(tmema), may further disperse the protonema. Usuallyshoot stage of the moss. Usually, numerous shootsmeristem. Divisions occurring in the apical cell formto a single leaf and a portion of the stem. The angle of and are phyllotaxy, and Tetraphishave leaves aligned in three rows, a phyllotaxy. Inmost mosses, however, the leaves are spirally distributed, and phyllotaxies being most common (W. Frey1971; B. Crandall-Stotler 1984). Branches, whichmorphology as compared to the later-formed leaves.macronemata, respectively, are found at the branch base,groups, namely, acrocarps and pleurocarps, based on the(Fig. 1). Acrocarps are characterized by erect or ascendingsparingly branched. Branching is typically sympodialinnovations. Pleurocarps are generally characterized bypositions all along the primary stem. Cladocarpic mossesas the vegetative branches. Such branches are themselvesacrocarpic nor pleurocarpic (La Farge). Althoughtrue mosses (B. Goffinet and W. R. Buck 2004), butAcrocarpy, which appears to be the plesiomorphiccondition, also characterizes the Takakiopsida,Andreaeopsida, and Andreaeobryopsida. The main stems (Superclass II) display a furcate orbranches per fascicle. At least two branches in eachwhile one to three are divergent. Despite their distinctive is like that of other mosses, with each brancharising from a single axillary bud initial (Leitgeb). Atcapitulum. Archegonia terminate special, short branchesTakakia and brown rhizoids. As in caulonemata, the rhizoids aresmooth or roughened with papillae. Rhizoids can be 6MORPHOLOGYbecome starch-filled and hyaline toward the stem interior.assimilates. The central strand, absent in some taxa, isalways a solid core of nonlignified, water-conductinghydroids. Hydroid structure varies among taxadiameter, thin-walled hydroids of most taxa. In addition,leptoids. These more specialized cells function in the2). These small clusters of hydroids may remain only in FIGURE 2. Stem anatomy, paraphyllia, pseudoparaphyllia and variations in leaf morphology and arrangement. retort cells. The living cells to the inside of the epidermisVariation also occurs in the formation of externalstructures that are associated with stems. The stemalong the stem. Pseudoparaphyllia are additionalstructures found only in pleurocarps. Althoughformed only at the bases of branches. They likely serve 8MORPHOLOGYoblate, can be found in either group. Usually, cell shapesand sizes are not uniform throughout the leaf. Inparticular, the cells near the leaf base are comparativelystill smaller cells occur at the leaf apex. The basal cellsof the lamina (Fig. 1). Sometimes this zone ofto the costa. Hyaline alar cells that are inflated and thin-downward during dry conditions. Laminal cells arevariety of wall projections called papillae (Fig. 3). Papillaeare heterogeneous in form, size, and distribution. Theymay be solid or hollow, simple or branched, single oror prorulose). Various types of epicuticular wax depositsmay add to this ornamentation (M. C. F. Proctor 1979). FIGURE 4. Variation in leaf morphology and types of asexual diaspores. In pattern differ between the main stem and branches. In Tetrodontium protonema produce leaflike flaps and in suite of taxonomically useful characters (Fig. 3). Leaves(excurrent). In a few acrocarps and many pleurocarps,and double, or absent (Fig. 1). Costa anatomy is variablewith several distinctive patterns (I. Kawai 1968). Thethan the internal cells. Often, a row of large, thin-walledoccasionally, there will be a small strand of hydroidsoccur. As suggested by the abundance of stereids in mostalso function in transport. The guide cells of the costa 10MORPHOLOGYantheridia swell and open at their apices. Drops of rain2006). Slimy mucilage secretions in the archegonial neckshelp pull the sperm downward to the egg. Fertilizationcell divisions in the surrounding archegonial center, basalproduce an enclosing epigonium. Early in development,part of the epigonium. Both organic nutrients and waterthe placenta. A stemlike seta is differentiated above theapical cell at the apex of the sporophyte. Theepigonium. The basal part of the epigonium, which stillremains over the tip of the sporophyte is the calyptra. Inruptures the epigonium. In a few mosses, e.g.,2001, fig. 25A). Variation in the timing of epigonialcapsule until spore maturation is complete. Calyptraeare of two types based on form. The cucullate type is slitthe base. Variations in calyptra shape, size, areolation,characters, as detailed by P. Janzen (1916).resulting in polysety, or multiple setae emerging from aAnatomically, the seta resembles the stem of thecentral conducting strand. There is always a waxy,C. Wiencke 1976; C. Hébant 1977). Prior to capsulecells and stereids. It is not uncommon for the interiora hollow seta (W. Lorch 1931; Hébant). In most mosseswith papillae or bristly outgrowths. Often, the epidermalrehydrated. The direction and pattern of the twist istaxonomically useful in some groups. The extent of setafoot. This extended gametophytic tissue is called acapsule. Very early in development, periclinal divisionsin the apically produced capsule initials separate an inner,With the exception of amphithecium. Details of these later stages in capsuleincluding, among others, F. Kienitz-Gerloff (1878),Variations in the morphology of the mature capsule(Fig. 5). Capsules vary in shape from spheroid to ovoid, 12MORPHOLOGYslitlike opening in a single cell. In but there are no stomata associated with them. Variationsin number, form, and distribution of stomata aretaxonomically informative (J. A. Paton and J. V. PearceInternally, the central strand of the seta extends upwhich the stoma open. This is a major site ofgrowth (M. C. F. Proctor 1977).the urn to the operculum of the capsule. The oftenelongate spore sac encircles the columella. To the outsideand the thick-walled exothecium. In Polytrichopsida, aduring capsule dehiscence. Annulus anatomy variesstructure of the cells comprising it. In its simplest form,the neighboring exothecial and opercular cells. This typeof its cells compared to the neighboring cells. This is the. In many and hydrophobic walls (Fig. 1). During dehiscence, theinternal cells swell with the uptake of water, but the outercells remain unchanged. This differential swelling causesrevoluble annulus. In either case, removal of thethe operculum. The developmental history andsystematic characters (Fig. 5). Peristomes are of twofound only in Polytrichopsida and Tetraphidopsida, andarthrodontous. In a nematodontous peristome, the teethcolumella called the epiphragm. The release of thewhich the spores are slowly released. In theTetraphidopsida, there are four erect, wedge-shapedof paired, periclinal cell walls. As reviewed by severalH. Robinson 1984; W. R. Buck and B. Goffinet 2000),2) in the apex of the embryonic capsule. Following(PPL), and inner peristomial layers (IPL). The number slice of a transversecapsule with 32 OPL, 16 PPL, and 24 IPL cells. Thenamely, haplolepidous and diplolepidous (Fig. 5). Thewalls of the PPL and IPL. The peristomial formula isConsequently, the outer surface of the tooth, which may(= vertical cell walls). The teeth can be forked at their32 long narrow, filaments, e.g., the Pottiaceae.