Solitary bodies (S-bodies) in the parasitic red algaHarveyella mirabilis (Choreocolaceae,Cryptonemiales)

Summary Unusual spherical cytoplasmic inclusions identical to S-bodies described previously in three angiosperms were found in all cells of the parasitic red algaHarveyella mirabilis collected from several locations in the northeast Pacific. The inclusions are ca. 60–80 nm and consist of an outer double membrane bounding a granular mantle and a DNase sensitive central core. S-bodies are dispersed throughout the cytoplasm and are associated occasionally with nuclei, plastids, mitochondria, ER, and vacuoles. They have not been observed in any other alga except in host algal cells, connected to parasite cells by cellular pit connections. The possible function of these inclusions is considered with respect to the parasitic nature ofHarveyella mirabilis.     

Microgametogenesis in Plumbago zeylanica (Plumbaginaceae). 1. Descriptive cytology and three-dimensional organization

The generative cell is initiated as a small, lenticular, unpolarized cell with a cell wall traceable to two origins: the external segment originates as intine, while an inner callose positive cell wall forms de novo. As the lenticular generative cell begins its migration into the pollen cytoplasm, the generative cell becomes polarized both externally and internally, displaying a characteristic shape and patterns of organelle distribution oriented with respect to the vegetative nucleus and independent of pollen aperture location. Separation of the generative cell from the pollen wall begins at the end opposite the vegetative nucleus and results in an elongating protuberance at the opposite end of the generative cell; this becomes associated with a preformed groove located on the surface of the vegetative nucleus. The generative cell subsequently separates from the intine near the vegetative nucleus and moves progressively toward the opposite end of the cell; during this separation, the edge of the wall facing the intine becomes callose-positive and remains so until separating from the intine. The generative cell becomes a free cell within the pollen, which is in physical association with the vegetative nucleus. Generative cell organization and organelle content become increasingly polarized during maturation, with microtubules evident both in the elongating protuberance of the generative cell and in association with organelles. The generative nucleus migrates away from the vegetative nucleus and toward the plastid-rich end of the generative cell, whereas mitochondria are more generally distributed within the cell. Generative cell polarization is made permanent during mitotic division and cytokinesis, i.e., two sperm cells differing in morphology are formed: the larger cell associated with the vegetative nucleus (S_vn) contains a majority of the mitochondria, and the smaller, unassociated sperm cell (S_ua) receives the plastids.     

REPRODUCTIVE DEVELOPMENT OF THE PARASITIC RED ALGA GARDNERIELLA TUBERIFERA (SOLIERIACEAE,GIGARTINALES)1

Examination of the reproductive morphology of the adelphoparasitic red alga Gardneriella tuberifera Kylin reveals that this monotypic genus is correctly placed in the family Solieriaceae (Gigartinales), to which its host Agardhiella gaudichaudii (Montagne) Silva et Papenfuss also belongs. Gardneriella is multiaxial, nonprocarpic and has an inwardly directed, three-celled carpogonial branch. The large, reniform uninucleate auxiliary cell is distinct prior to and after fertilization. It is diploidized by an unbranched, multicellular connecting filament which lacks pit connections. One or two connecting filaments arise from each fertilized carpogonium. From the diploidized auxiliary cell, the gonimoblast initial is cut off obliquely toward the interior of the thallus. The cells of the gonimoblast fuse with adjacent unpigmented vegetative cells of Gardneriella and pigmented cells of the host. These cells become incorporated into the developing cystocarp and, from those of Gardneriella, additional short chains of gonimoblast cells arise. The mature cystocarp is placentate, radiately lobed, and lacks a surrounding involucre. Carposporangia are borne in short chains and the unpigmented carpospores are released upon the dissolution of outer vegetative cells. No ostiole is present. Gardneriella appears to be most closely related to the placentate solieriacean genera Agardhiella, Sarcodiotheca, and Meristiella and therefore this genus should be placed in the tribe recently erected for these taxa, the Agardhielleae.     

THE BIOLOGY OF HARVEYELLA MIRABILIS (CRYPTONEMIALES; RHODOPHYCEAE). V. HOST RESPONSES FO PARASITE INFECTION1,2

The thallus of Harveyella mirabilis (Reinsch) Schmitz & Reinke is composed of vegetative rhizoidal cells growing intrusively between adjacent cells of the red algal hosts (Odonthalia and Rhodomela) and a protruding reproductive pustule. Although primarily composed of Harveyella cells, host medullary and cortical cells also occur in the emergent pustule. In both tissue regions, Harveyella cells are connected to host cells by secondary pit connections initiated by the host. Direct penetration of host cells by rhizoidal cells of Harveyella occasionally occurs, resulting in host cell death. Degeneration of host medullary cells beneath the pustule may result in a hollow branch and the cortical cells undergo cell division forming a thick palisade layer of randomly associated, photo-synthetically active cells. It is within these branches that the parasite overwinters vegetatively. Host medullary and cortical cells dispersed in the emergent pustule show few of the degenerative responses noted in host cells adjacent to parasite rhizoidal cells. Rather, host cell division, chloroplast division and photosynthetic assimilation of H¹⁴CO^?₃ all increase. Spherical virus-like solitary bodies (S-bodies) occur in all Harveyella cells and in all host cells attached to Harveyella by secondary pit connections. The possibility that these structures may induce the infective response in the host is discussed.     

The structure and formation of host-parasite pit connections between the red algal alloparasiteHarveyella mirabilis and its red algal hostOdonthalia floccosa

Summary Harveyella mirabilis is a colourless red algal alloparasite which grows on and within its photosynthetic hostOdonthalia floccosa. Cells ofHarveyella establish secondary pit connections (PCs) with other parasite cells and with cells of the host. Small, uninucleate conjunctor cells are produced by parasite cells and remain connected to them by PCs. Conjunctor cells may fuse with either an adjacent host or parasite cell, with the parasite-conjunctor cell PC becoming either a host-parasite or parasite-parasite secondary PC. Occasionally the conjunctor cell does not fuse with an adjacent cell (either host or parasite) and degenerates. The secondary pit plug which forms between a parasite cell and its conjunctor cell always develops with two structurally distinct surfaces characteristic of a host-parasite pit plug. Only if the conjunctor cell fuses with another parasite cell will the structure of the pit plug be altered to that of a parasite-parasite pit plug. Fungal hyphae also invade the region of infection, andHarveyella cells respond by producing nonfunctional conjunctor cells that grow towards adjacent hyphae. Evidence suggests that secondary PCs may be induced to form mechanically, by the physical presence of another cell, rather than in direct response to a message received from an adjacent cell. The mechanism of secondary PC formation described here is similar to that reported for the closely related alloparasiteHolmsella and may be common to a number of red algal parasitic associations. Helen Margaret Quirk, B. Sc. (Hons), M. Sc. (1953–1982), student, research assistant and friend, died after a long illness on October 24, 1982.     

CHOREONEMA (CORALLINALES, RHODOPHYTA): 18S rDNA PHYLOGENY AND RESURRECTION OF THE HAPALIDIACEAE FOR THE SUBFAMILIES CHOREONEMATOIDEAE, AUSTROLITHOIDEAE, AND MELOBESIOIDEAE

Phylogenetic analyses of 18S rDNA gene data for Choreonema thuretii (Corallinales, Rhodophyta) and available data for other coralline red algae indicated that Choreonema belongs to the same lineage as other taxa of Corallinales possessing tetra/bisporangial conceptacles with multiporate plates. These results, when integrated with extant morphological/anatomical data, ultrastructural data, and taxonomic data led to the conclusion that all taxa of Corallinales possessing multiporate conceptacles belong to a distinct family, the Hapalidiaceae. Recognition of the Hapalidiaceae as a distinct family was supported both phylogenetically and phenetically. The Hapalidiaceae includes those taxa of Corallinales whose tetrasporangia produce zonately arranged spores and whose tetra/bisporangia are borne in conceptacles, produce apical plugs, and develop beneath multiporate plates. The Hapalidiaceae includes the subfamilies Choreonematoideae, Melobesioideae, and Austrolithoideae, formerly placed in the Corallinaceae sensu lato . The Choreonematoideae lack cell connections between adjacent vegetative filaments and have a multiporate plate that is acellular at maturity, consisting only of a calcium carbonate matrix. The Austrolithoideae and Melobesioideae both have cellular pore plates; taxa of Melobesioideae have cell fusions between cells of adjacent vegetative filaments, whereas taxa of Austrolithoideae lack cellular connections between adjacent vegetative filaments. Inclusion of the Austrolithoideae in the Hapalidiaceae was based entirely on morphological/anatomical evidence; molecular evidence currently is lacking. Relevant historical and nomenclatural data are included.     

Development of the red algal parasite Vertebrata aterrimophila sp. nov. (Rhodomelaceae,Ceramiales) from New Zealand

Parasitic red algae grow only on other red algae and have over 120 described species. Developmental studies in red algal parasites are few, although they have shown that secondary pit connections formed between parasite and host and proposed that this was an important process in successful parasitism. Furthermore, it was recorded that the transfer of parasite nuclei by these secondary pit connections led to different host cell effects. We used developmental studies to reconstruct early stages and any host cell effects of a parasite on Vertebrata aterrima. A mitochondrial marker (cox1) and morphological observations (light and fluorescence microscopy) were used to describe this new red algal parasite as Vertebrata aterrimophila sp. nov. Early developmental stages show that a parasite spore connects via secondary pit connections with a pericentral host cell after cuticle penetration. Developmental observations revealed a unique connection cell that grows into a ‘trunk-like’ structure. Host cell transformation after infection by the parasite included apparent increases in both carbohydrate concentrations and nuclear size, as well as structural changes. Analyses of molecular phylogenies and reproductive structures indicated that the closest relative of V. aterrimophila is its host, V. aterrima. Our study shows a novel developmental parasite stage (‘trunk-like’ cell) and highlights the need for further developmental studies to investigate the range of developmental patterns and host effects in parasitic red algae.     

LEACHIELLA PACIFICA,GEN. ET SP. NOV., A NEW PARASITIC RED ALGA FROM WASHINGTON AND CALIFORNIA

Leachiella pacifica, gen. et sp. nov., a marine alloparasitic red alga is described from Washington and California. Several species of Polysiphonia and Pterosiphonia are hosts for this parasite. The thallus is a white, multiaxial, unbranched pustule with rhizoidal filaments that ramify between host cells, forming numerous secondary pit connections with host cells. All reproductive structures develop from outer cortical cells. Tetrasporocytes, situated on stalk cells, undergo simultaneous, tetrahedral cleavage to form tetraspores. Spermatia are formed continuously by oblique cleavages of the elongate spermatial generating cells. This results in spermatial clusters consisting of 4–8 spermatia in an alternate arrangement. Carposporophyte development is procarpial. The carpogonium is part of a six-celled branch including a sterile cell that is formed by the basal cell. The carpogonial branch is attached laterally to an obovate supporting cell that also forms an auxiliary cell, presumably formed prior to fertilization. After fertilization the carpogonium temporarily fuses with the auxiliary cell apparently to transfer the diploid nucleus and initiate further fusion with the subtending supporting cell to form an incipient fusion cell. The auxiliary cell portion of this fusion cell divides to form gonimoblast initials that continue to divide, forming gonimoblast filaments whose terminal cells differentiate into carpospores. The remainder of the fusion cell enlarges by continual fusion with adjacent vegetative cells. The resultant carposporophyte consists of a basal, multinucleate fusion cell supporting a hemispherical cluster of gonimoblast filaments with terminally borne carpospores. Vegetatively, Leachiella resembles several other parasitic red algae but it is clearly separated by the procarp, carposporophyte development and structure, and tetrasporocyte cleavage.     

THE ROLE OF SECONDARY PIT CONNECTIONS IN RED ALGAL PARASITISM1

Secondary pit connections are common between cells of hosts and parasites in the widespread phenomenon of red algal parasitism. The DNA-specific fluorochrome 4′,-6-diamidino-2-phenylindole (DAPI) reveals that in host-parasite secondary pit connection (SPC) formation between the parasitic red alga Choreocolax polysiphoniae and its host Polysiphonia confusa, a nucleus and other cytoplasmic components of the parasite are delivered into the cytoplasm of a host cell. Host cells receive large numbers of parasite nuclei and these, apparently arrested in G¹, are maintained intact in host cells for periods of several weeks. Within these enlarged, differentiated cells, starch accumulates and cytoplasmic organelles proliferate as the central vacuole decreases in size. Host nuclear DNA synthesis is stimulated in the infected host cell, resulting in an increase in the number of host nuclei, or an increase in DNA in each of the existing host nuclei (i.e. somatic polyploidy). Occasionally, infected host cells will recommence division and engender a new host branch. Microspectrofluorometry of nuclear DNA quantitatively confirms not only the identity and transfer of parasite nuclei to host cells, but also the transfer of parasite nuclei to other parasite cells. Measurements also reveal that the single nucleus of Choreocolax becomes progressively more polyploid as cells become larger and more highly differentiated. Secondary pit connection formation between Choreocolax and Polysiphonia provides the mechanism for the transfer of parasite genetic information (via the parasite nucleus and cytoplasm) into the host. The parasite nuclei may thereby control and redirect the physiology of the host for the benefit of the parasite.     

Quantitative cytology of the sperm cells of Brassica campestris and B. oleracea

Pollen grains of Brassica campestris L. var. acephala DC and B. oleracea L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and mitochondrial content. The larger of the two sperm cells (S_vn) is distinguished by the presence of a blunt evagination, which in B. oleracea wraps around and lies within shallow furrows on the vegetative nucleus and in B. campestris can penetrate through internal enclaves of the vegetative nucleus. This sperm cell contains more mitochondria in both species than the second sperm cell (S_ua). This latter cell is linked to the first by a common cell junction with the S _vn, but is not associated with the vegetative nucleus and lacks a cellular evagination. Such differences are indicative of a system of cytoplasmic heterospermy in which sperm cells possess significantly different quantities of mitochondria.Abbreviations mtDNA mitochondrial DNA - S_ua sperm cell unassociated with the vegetative nucleus - S_vn Sperm cell physically associated with the vegetative nucleus     

Host-parasite relations betweenAllomyces andRozella

Summary Zoospores of the obligately parasitic chytridRozella allomycis encyst all over the hyphae of a susceptible host, the water-moldAllomyces arbuscula, but many of them fail to penetrate. At the sites of successful penetration lomasomes occur, and the inner layer of the host cell-wall grows and invaginates around a papilla, through the center of which the parasite enters. This host response resembles instances of normal, localized inward growth of fungal cell-walls. The response may also be related to a defense reaction of walled cells which form callosities to block the invasion of fungi.Rozella appears to utilize this response and to depend upon it—probably in order to enter the host cell with minimal disruption. A similar relationship may control the penetration of various obligately parasitic plant-pathogens into their hosts.     

CONCEPTACLE STRUCTURE OF THE PARASITIC CORALLINE RED ALGA CHOREONEMA THURETII (CORALLINALES) AND ITS TAXONOMIC IMPLICATIONS1

The major diagnostic features for erecting the red algal subfamily Choreonematoideae (Corallinales) were a combination of 1) absence of both cell fusions and secondary pit connections, 2) conceptacle roof and wall comprised of a single cell layer, and 3) presence of tetrasporangial pore plugs within a uniporate conceptacle in the monotypic taxon Choreonema thuretii (Bornet) Schmitz. Because this alga is a parasite, the absence of secondary cell connections is most likely an adaptation to a reduced thallus. This study shows that all conceptacles are not composed of a file of cells but rather a single layer of epithallial cells that are underlain by a thick layer of calcified acellular material; both epithallial cells and the calcified layer are produced by peripheral sterile cells. Although the outermost tetrasporangial pore canal is uniporate, there is a calcified acellular multiporate plate recessed just below the rim. The plate is produced by interspersed sterile cells and is continuous with the calcified layer supporting the conceptacle. These unique structures are likely due to parasitism rather than to the ancestral state. Based on these results and a reexamination of published micrographs depicting lenticular cells in Austrolithon intumescens Harvey et Woelkerling, we propose that both subfamily Choreonematoideae and Austrolithoideae are closely allied with subfamily Melobesioideae. This distant relationship to its host (Corallinoideae) plus a combination of unique conceptacle and unusual type of parasitism indicates that C. thuretii is an alloparasite and that it is likely the most ancient red algal parasite studied to date.     

Lithophyllum cuneatum sp. nov. (Corallinaceae, Rhodophyta), a new species of non-geniculate coralline alga semi-endophytic in Hydrolithon onkodes and Neogoniolithon sp. from Fiji, South Pacific

A new species of semi-endophytic coralline alga, Lithophyllum cuneatum (Corallinaceae: Lithophylloideae), is described from Fiji. The species is characterized by a wedge-like thallus that is partially buried in the thallus of the host coralline, Hydrolithon onkodes (Heydrich) Penrose et Woelkerling or occasionally Neogoniolithon sp., and that appears at the surface of the host as a small pustule that is usually paler in color than the host. The thallus consists of erect filaments that are derived from a single cell. The basal cell, when visible, is non-palisade, and areas of bistratose margin are absent. Cells of contiguous erect filaments are joined by secondary pit connections. Epithallial cells are present in 2–3 layers, and individual trichocytes are common. Gametangial plants are dioecious. Male conceptacles have simple spermatangial systems that are confined to the floors of their elliptical chambers. Carposporangial conceptacles contain 5–8 celled gonimoblast filaments that are borne at the margin of a more-or-less discoid fusion cell, and so occupy the periphery of the elliptical conceptacle chambers. Tetrasporangial conceptacles are uniporate, with roofs formed from peripheral filaments, and chambers lack a central columella of sterile filaments. Despite its semi-endophytic nature, haustorial cells are absent, and plastids and pigmentation are present.     

The fine structure of secondary pit connection formation between the red algal alloparasiteHolmsella australis and its red algal hostGracilaria furcellata

Summary Pit connections (PCs) develop between the parasitic red algaHolmsella and its hostGracilaria. Only parasite cells initiate the formation of host-parasite pit connections. The parasite produces a small connecting cell (termed the conjunctor cell) which moves through the cell wall to fuse with either an adjacent host or parasite cell. The parasite secondary PC, which forms between the conjunctor cell and the parasite cell, is structurally different from a parasite primary PC, and has the distinct structure of a host-parasite PC. Only if the conjunctor cell fuses with another parasite cell will the former parasite-conjunctor cell PC be altered to a typical parasite-parasite PC. If the conjunctor cell fuses with an adjacent host cell the PC continues to develop as host-parasite. Occasionally a conjunctor cell fails to fuse with an adjacent cell (whether host or parasite), and the conjunctor cell and PC eventually breakdown in the cell wall. The parasite overcomes several barriers in order to infect the host, including the formation of host-parasite PCs which appear to be a necessary component of the parasiticHolmsella-Gracilaria association.     

The fine structure and cytology of the association between the parasitic red algaHolmsella australis and its red algal hostGracilaria furcellata

Summary Holmsella australis Noble andKraft ms. is a colourless red algal parasite, forming whitish pustules on its photosynthetic red algal host,Gracilaria furcellata Harvey. In the infected region, host cortical tissue continues to grow and enclose the expanding pustule. Filaments of both host and parasite grow apically, the cells being connected by primary pit connections (PCs). Secondary PCs form between cells of the same species, and in addition,H. australis initiates the formation of secondary PCs with cells ofG. furcellata. All three types of secondary PC are morphologically distinct. In hostparasite PCs the surface adjoining the host cell is similar in structure to a host-host PC, while that adjoining the parasite cell has the structure of a parasite-parasite PC. The plasma membrane is continuous between the cells of the unrelated host and parasite. In addition, a cap membrane is typically produced only on the host surface, though occasionally the parasite side is enclosed by a cap membrane as well. Cap membranes are absent from parasite-parasite PCs (making them intracellular), while host-host PCs are typically extracellular, both cells producing cap membranes. The presence or absence of a cap membrane in certain positions appears to vary, and suggests that cells may be able to regulate its presence. Since transport of nutrients would be expected to occur from host to parasite cells, and between parasite cells, the morphological evidence presented here suggests the PCs may be the pathway.     

Brassica napus pollen development during generative cell and sperm cell formation

Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.     

Anatomical relations among endophytic holoparasitic angiosperms, autotrophic host plants and mycorrhizal fungi: A novel tripartite interaction

Mycorrhizae are widespread mutualistic symbioses crucial for the functioning of terrestrial ecosystems. Not all plants associate with mycorrhizae; most parasitic plants have been suggested to be nonmycorrhizal because they have developed alternative strategies to obtain nutrients. In endophytic parasitic plants, whose vegetative bodies grow completely inside their mycorrhizal host roots, the opportunity for establishing a tripartite association seems evident, but information on these systems is lacking. In studying natural associations among the endophytic holoparasite Cytinus hypocistis, their Cistaceae host species, and associated mycorrhizal fungi, we found that mycorrhizae were associated with the hosts and the parasites, reaching high frequencies of colonization. In parasitic and host root tissues, mycorrhizal fungi spread in the parenchymatic cells by intracellular growth and formed hyphal coils and vesicles, while the cambium and the vascular tissues were never colonized. This report is the first on a tripartite association of an endophytic parasitic plant, its host, and mycorrhizae in natural conditions, representing a novel trophic interaction not previously reported within the angiosperms. Additional studies on the interactions occurring among these three players are needed because they may be crucial to our understanding of how this mutualistic-antagonistic system is functioning and evolving.     

DEVELOPMENT OF JANCZEWSKIA MORIMOTOI (CERAMIALES) ON ITS HOST LAURENCIA NIPPONICA (CERAMIALES,RHODOPHYCEAE)1

Janczewskia morimotoi Tokida was successfully cultured from spore to reproductive maturity on its host Laurencia nipponica Yamada. The spore penetrates the host without requirement for wound or abrasion sites, growing between host cortical cells and developing a superficial and an endophytic system simultaneously. During the juvenile period, when the parasite is nonpigmented, it differentiates a cortex and the proliferating endophytic filaments enlarge causing a displacement of layers of host cells into the parasitic tissue. Host cells contacted by cells of the parasite exhibit increased wall thickness, cytoplasmic density and vesicle formation. Pit connections between host and parasite cells were rarely observed whereas penetration of host cell walls was seen commonly. As the parasite increases in size, its cells become pigmented evenly throughout the cortex and host cells show less obvious reactions to the parasite. At this same time, the parasite develops branches and reproductive structures. Host plant segments less than 3 cm long failed to grow when infected with spores of the parasite whereas longer segments were not significantly affected by the parasite. In the absence of the host, the parasite cannot complete its development. Although J. morimotoi is well pigmented at maturity, the absence of pigmentation in the juvenile stage, penetration of host cells, and effect on host growth in culture strongly suggest that it is parasitic during at least its early development.     

DEVELOPMENT OF THE CARPOSPOROPHYTE OF KALLYMENIA RENIFORMIS (TURNER) J. AGARDH1

The development of the carposporophyte in Kallymenia reniformis involves an elaborate series of interactions between reproductive and vegetative tissues. Following fertilization, the inner cells of the carpogonial branches form processes that unite with the supporting cell and with each other, giving rise to a large fusion cell. A number of medullary filaments are enveloped and incorporated within the developing fusion cell. Secondary filaments may be produced from medullary cells outside the fusion cell after connecting filaments have been initiated. Connecting filaments are nonseptale and wind their way through the medulla. The presence of a connecting filament in the vicinity of an auxiliary cell appears to initiate a complex sequence of responses. Vegetative filaments are produced in the medulla and inner cortex that grow centripetally toward the auxiliary cell and fuse with one another, forming a network of secondary tissue. One of the vegetative cells may penetrate the auxiliary cell, while others intrude into subsidiary cells connecting them with the network. An ostiolate pericarp is initiated in the cortex above the auxiliary cell. The connecting filament fuses with the auxiliary cell and also with some of the surrounding vegetative cells, forming an irregular lobed structure. Gonimoblast is initiated in scattered pockets from vegetative cells in the vicinity of the auxiliary cell apparatus.     

The occurrence of Ezo epiyessoense Adey,Masaki & Akioka (Rhodophyta,Corallinaceae) in England with a summary of parasitism and endophytism in nongeniculate Corallinaceae

The parasitic, nongeniculate, coralline red alga Ezo epiyessoense (Rhodophyta, Corallinaceae) was described in 1974 by Adey, Masaki & Akioka on the basis of specimens growing on Lithophyllum yessoense in Japan. The authors considered Ezo to be an adelphoparasite because it resembled its host taxonomically in being a member of the coralline subfamily Lithophylloideae. The species had not been recorded outside Japan until the present observation in England where it was found growing on another lithophylloid species, Titanoderma pustulatum. The structure of the English material of E. epiyessoense is described and shown to closely resemble that of the type material despite its occurrence on a different host species. Tetrasporangia and trisporangia are recorded for the first time in Ezo. A summary is given of known nongeniculate coralline parasites, semi-endophytes and outgrowths.