A structural comparison of cyst and germ tube wall inPhytophthora palmivora

Summary An electron microscopic analysis of germinating cysts ofPhytophthora palmivora involving freeze-etching, thin sectioning, and replica techniques reveals that both cyst and hyphal wall comprise a two-phase system with a fibrillar and an amorphous component. The cyst wall is fibrillar throughout with the fibrils tightly interwoven and embedded in an amorphous matrix on the internal side of the wall. The hyphal wall consists of a fibrillar inner layer with the fibrils lightly covered by some amorphous material and an amorphous outer layer devoid of any fibrillar material. Both cyst and germ tube walls are wholly or partially covered by a fluffy coat of variable thickness. In the zone of germ tube emergence cyst wall and germ tube wall overlap and are tightly apposed. Thus, the germ tube wall is not a simple extension of the cyst wall but a new structural entity separated from the cyst wall by a thin line of demarcation.     

Regeneration of the cell wall in protoplasts of Candida albicans

To assess the dynamics of synthesis of the wall by regenerating Candida albicans protoplasts deposition of chitin and mannoproteins were investigated ultrastructurally using wheat germ agglutinin conjugated with either horseradish peroxidase or colloidal gold, and Concanavalin A coupled to ferritin respectively.Freshly prepared protoplasts lacked wheat germ agglutinin receptor sites but after 1–2 h of regeneration, they were detected. After 4–5 h of regeneration, the cell wall showed a discrete structure which was only labelled with wheat germ agglutinin in thin sections. At this stage of regeneration the outermost layer of the wall was labelled with clusters of Concanavalin A-ferritin particles.After 8 h regeneration, the cell wall appeared compact, and homogenously marked with wheat germ agglutinin whereas only the surface layers appeared consistently labelled with Concanavalin A-ferritin.From these observations we conclude that C. albicans protoplasts are able to regenerate in liquid medium a cell wall consisting of a network of chitin fibrils and mannoproteins at least (glucan polymers were not determined in the present cytological study). The former are the fundamental component of the inner layers at early stages of regeneration, whereas the latter molecules are predominant in the outer layers of the wall.Abbreviations WGA-HRP wheat germ agglutinin conjugated with horseradish peroxidase - WGA-Au wheat germ agglutinin conjugated with colloidal gold - Con A-ferritin Concanavalin A coupled to ferritin     

Localization of chitin on ultrathin sections of cysts of two ciliated protozoa,Blepharisma undulans andPseudomicrothorax dubius,using colloidal gold conjugated wheat germ agglutinin

Summary The cyst walls of the ciliatesBlepharisma undulans andPseudomicrothorax dubius were examined ultrastructurally and by postembedding labeling with wheat germ agglutinin (WGA)-gold conjugate. Different methods of fixation and embedding were performed. In all procedures, WGA-gold binds selectively to material of the cyst wall. Pretreatment of the sections with chitinase inhibits labeling. The cyst walls of both species contain 3 nm fibrils, which are supposed to be of chitinous nature. In the cyst wall ofB. undulans, several thin layers of WGA-binding fibrils are interspaced with thick layers of other material. InP. dubius, WGA-binding sites are mainly concentrated in the mesocyst, where the microfibrils appear to represent the major component. These results obtained from two phylogenetically distant species confirm that chitin synthesis is an ancestral feature of ciliated protozoa. The amount and distribution of the chitin fibrils may play an important role in the properties and functions of the wall of the resting cyst.     

Untersuchungen über den chemischen Aufbau von Sporen- und Keimschlauchwänden der Uredosporen des Weizenrostes (Puccinia graminis var. tritici)

Zusammenfassung Zellwände und Keimschläuche von Uredosporen des Weizenrostes (Puccinia graminis var. tritici) wurden isoliert, und ihre chemische Zusammensetzung wurde quantitativ untersucht. Als gemeinsame Bausteine enthalten Sporenwände und Keimschlauchwände Proteine, Lipide und die Neutralzucker Galaktose, Glucose und Mannose. Die einzelnen Komponenten liegen in unterschiedlicher Menge vor. Auch qualitativ unterscheiden sich die Sporenwände und die Keimschlauchwände: Melanin ist nur in den Sporenwänden vorhanden, in den Keimschlauchwänden dagegen nicht. Der polymer gebundene Aminozucker der Keimschlauchwände ist N-Acetylglucosamin, das mit großer Wahrscheinlichkeit als Chitin vorliegt. Die Sporenwände enthalten dagegen polymeres Glucosamin (vermutlich Chitosan).Sporenwände sind in 3% iger NaOH löslich. Aus diesem Extrakt läßt sich mit Fehlingscher Lösung ein Galaktoglucomannan fällen, das überwiegend aus Mannose besteht. Aus der entsprechenden Fraktion der Keimschlauchwände, in der ebenfalls Mannose überwiegt, kann mit Fehlingscher Lösung kein Mannan gewonnen werden. Der in NaOH unlösliche Satz der Keimschlauchwände ist zum größten Teil aus Glucose und N-Acetylglucosamin aufgebaut. Es gibt keine identischen Polysaccharidfraktionen von Sporen- und Keimschlauchwänden. Sie sind heteropolymer und setzen sich jeweils aus Galaktose, Glucose und Mannose zusammen.

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Investigations on the chemical composition of spore walls and germ tube walls of wheat rust (Puccinia graminis var. tritici) uredospores

Summary Spore walls and germ tube walls from uredospores of wheat stem rust (Puccinia graminis var. tritici) were isolated and their chemical compositions determined quantitatively. The spore and germ tube walls are commonly composed of proteins, lipids, and the neutral sugars mannose, glucose and galactose. Carbon and nitrogen content, total lipids, composition of bound amino acids, total glucosamine and chitin content, and neutral sugars of spore and germ tube walls were compared. While the carbon content of the germ tube walls is only slightly higher than that of the spore walls, the germ tube walls contain twice as much nitrogen and lipids as the spore walls. The higher nitrogen content of the germ tube walls is due to higher amounts of bound amino acids and hexosamine. The polymeric germ tube wall hexosamine is insoluble in 3% NaOH, while the bulk of the polymeric spore wall hexosamine will go into solution when treated with 3% NaOH. The polymeric amino sugar of the germ tube wall is N-acetylglucosamine, which in all probability is present as chitin. In comparison, spore walls contain polymeric glucosamine (probably chitosan).The predominant neutral sugar of the spore walls is polymeric mannose (90%) while the germ tube walls contain polymeric glucose and mannose in nearly equal amounts. Galactose occurs in both wall types as a minor constituent.From spore walls completely dissolved in 3% NaOH we were able to precipitate a galactoglucomannan with fehling's solution. This galactoglucomannan was composed mainly of mannose. The corresponding fraction of the germ tube wall gave no precipitate with Fehling's solution. An alkali insoluble fraction of the germ tube wall consists mainly of glucose and N-acetylglucosamine. There are no identical polysaccharide fractions in spore walls and germ tube walls. They are always heteropolymers. Melanine is found in spore walls but not in germ tube walls.

     

Early development in an algal gametophyte: role of the cytoskeleton in germination and nuclear translocation

Summary Biflagellate zoospores from the giant kelpMacrocystis pyrifera underwent germination after adhering to a substrate and produced germ tubes that were approximately 13–15 m in length. Coincident with the germ tube elongation was organelle (other than the nucleus) translocation along the tube. Shortly after formation of the germ tube, the zoospore nucleus divided and one daughter nucleus translocated along the germ tube. The nucleus did not appear to undergo chromosomal condensation prior to division. The nuclear division and/or translocation of the daughter nucleus did not begin until well after germ tube elongation was complete, demonstrating that these are temporally distinct developmental events. The translocation of one daughter nucleus coincided with differentiation of the distal end of the germ tube into a bulbous structure. Following this, the first gametophytic cross wall was formed and, subsequently, the daughter nucleus remaining in the original zoospore body underwent repositioning, assuming a position in the germ tube near the cross wall. Cytochalasin D inhibited germ tube elongation suggesting that actin microfilaments are probably involved in this developmental process. In addition, when cytochalasin D was added to the culture after the germ tube elongation was complete, it did not affect either nuclear division or translocation, indicating that microfilaments were not directly involved in these nuclear events. Colchicine and the plant specific microtubule disrupting agent, amiprophos methyl blocked nuclear division and translocation without affecting germination or germ tube elongation. These data suggest that actin microfilaments are primarily responsible for complete germination, specifically germ tube elongation, while microtubules are involved in nuclear division and translocation. The present study demonstrates that germination (and germ tube elongation) and nuclear translocation inM. pyrifera gametophytes are temporally and mechanistically distinct developmental events.     

Fine structure of germinatingPenicillium megasporum conidia

Summary Penicillium megasporum conidia have spore walls consisting of several layers. There is no visible change in the outer wall layers during spore germination, but the inner layers increases in thickness on only one side of the spore, resulting in a rupture of the outer wall layers and subsequently in germ tube formation. Invaginations in the plasma membrane disappear as the germ tube forms and emerges, and the nucleus migrates into the developing germ tube. Mitochondria gather at the base of the germ tube during its formation. During germination, the amount of lipid in the spore decreases and portions migrate into the germ tube. Membrane-bound, electron dense bodies are present in resting spores. These bodies decrease in size as germination proceeds, and the cytoplasm in the developing germ tube appears much more electron dense than the cytoplasm within the spore.     

Physiology and fine structure of sporangiospore germination in Piptocephalis unispora prior to infection

Germination of the sporangiospore of Piptocephalis unispora Benjamin, observed by means of light and electron microscopy, involved the formation of a new inner wall which became continous with the inner layer of the wall of the germ tube. The outer wall layer of the germ tube was continous with the original inner wall layer of the dormant spore. Preliminary details of appressorium structure were noted. Nutritional experiments indicated that sporangiospores required external sources of utilisable nitrogen and carbon compounds for maximal swelling and germ tube production. Limited development occurred when either nutrient was supplied singly. Comparison of germination of the asexual spore with that in other Mucorales, especially the Kickxellaceae, has been made, and the merosporangial status in P. unispora discussed.Non-Standard Abbreviations CH casein hydrolysate - Q spore quotient     

Wall texture in the spore of a vesicular-arbuscular mycorrhizal fungus

Summary InGlomus epigaeum Daniels and Trappe, a vesicular-arbuscular mycorrhizal fungus, the mature spore has a complex multi-layered wall containing a regular pattern of wall subunits.The outer wall (2–4 m thick) consists of a simple layer of parallel microfibrils. The inner wall (5–6 m thick) is built from two layers possessing different organization. The innermost layer, near the plasmalemma has a texture of apparently dispersed fibrils, whereas the second layer is regularly organized with an arced texture. Ten to twelve bundles of fibrils connected by apparently bow-shaped fibrils are consistently observed. The appearance of this arced organization depends on the section plane and on the angle of observation in the electron microscope as confirmed by tilting experiments. Wall subunits are evident as straight electron transparent fibrils; particularly well-defined in negatively stained frozen sections: their diameter is about 3.5nm.The regular pattern of wall subunits in this fungal cell wall is compared with the textures shown by cellulose fibrils in algae or higher plants and by chitin fibrils in arthropod cuticle.Research work supported by CNR, Italy. Special grant I.P.R.A.—Sub-project 1. Paper No. 55.     

Role of the conidium in dimorphism of Blastomyces dermatitidis

Fine details of yeastlike cell development of Blastomyces dermatitidis from its conidium are described and illustrated by electron micrographs. When cultured in an enriched medium at 37 °C, conidia of two strains of B. dermatitidis readily underwent ultrastructural changes consistent with mycelial to yeast dimorphism. Although hyphal cells contained in the conversion cultures were observed consistently to undergo profound degenerative changes, the conidia rapidly germinated to give rise to short germ tubes which subsequently enlarged to form intermediate yeast mother cells (YMC). The wall of the germ tube arose from the innermost layer of the wall of the germinant. During the transition globoid osmiophilic inclusions of unknown origin and function were observed in vacuolated areas of the germ tube and YMC cytoplasm. Yeastlike daughter cells then budded from the intermediate YMC. Since transformation was readily accomplished under in vitro conditions favoring mycelial to yeast dimorphism, it is suggested that the conidium of B. dermatitidis represents the primary infective unit of this pathogenic fungus.     

THE CELL WALL OF PYROCYSTIS SPP. (DINOCOCCALES)1,2

The cell of Pyrocystis spp. is covered by an outer layer of material resistant to strong acids and bases. Internal to this layer much of the cell wall is composed of cellulose fibrils. The presence of cellulose fibrils was established by staining raw and ultra-violet–peroxide-cleaned cell walls and by combining X-ray diffraction spectroscopy with electron microscope observation. Carbon replicas of freeze-etched preparations and thin sections of P. lunula walls show outer layers, inside them ca. 24 layers of crossed parallel cellulose fibrils (4–5 nm thick, ca. 12 nm wide), then a region of smaller (ca. 6–12 nm diameter) fibrils in a disperse texture, and then the plasma membrane. Cellulose fibrils in the parallel texture are constructed of 3–5 elementary fibrils ca. 3 nm in diameter. Walls of P. fusiformis and P. pseudonctiluca also have cellulose fibrils in a crossed parallel texture similar to those of P. lunula. The Gymnodinium-type swarmer from lunate P. lunula appears to have a cell wall ultrastructure typical of other “naked” dinoflagellates.     

Ultrastructure of the Wall of the Germinating Sporangiospore of Linderina pennispora (Mucorales)

Carbon replicas of germinating sporangiospores of Linderinapennispora show the outer wall complex to break open basally,during the phase of swelling, and the surface of the germ tubeto be smooth. Chemical treatment reveal the microfibrillar wallof the germ tube to be continuous with the microfibrillar innerwall complex of the spore. Microfibrils of the germ tube arerandornly arranged and appear to be finer than those of thespore wall. Ultra-thin sections reveal the wall of the germtube to consist of an outer electron-dense layer and an innermicrofibrillar electron-transparent layer and both layers originatein the basal region of the spore between the plasmalemma andthe inner wall complex of the spore.     

Participation of actin filaments,myosin and phosphatidylinositol 3‐kinase in the formation and polarisation of tetraspore germ tube of Gelidium floridanum (Rhodophyta,Florideophyceae)

• This study aimed to examine the evidence of direct interaction among actin, myosin and phosphatidylinositol 3‐kinase (PI3K) in the polarisation and formation of the tetraspore germ tube of Gelidium floridanum.
• After release, tetraspores were exposed to cytochalasin B, latrunculin B, LY294002 and BDM for a period of 6 h.
• In control samples, formation of the germ tube occurred after the experimental period, with cellulose formation and elongated chloroplasts moving through the tube region in the presence of F‐actin. In the presence of cytochalasin B, an inhibitor of F‐actin, latrunculin B, an inhibitor of G‐actin, and BDM, a myosin inhibitor, tetraspores showed no formation of the germ tube or cellulose. Spherical‐shaped chloroplasts were observed in the central region with a few F‐actin filaments in the periphery of the cytoplasm. Tetraspores treated with LY294002, a PI3K inhibitor, showed no formation of the tube at the highest concentrations. Polarisation of cytoplasmic contents did not occur, only cellulose formation.
• It was concluded that F‐actin directs the cell wall components and contributes to the maintenance of chloroplast shape and elongation during germ tube formation. PI3K plays a fundamental role in signalling for the asymmetric polarisation of F‐actin. Thus, F‐actin regulates the polarisation and germination processes of tetraspores of G. floridanum.

     

Electron microscopy of spore germination and cell wall formation in Mucor rouxii

Summary The fine structure of ungerminated and aerobically germinated sporangiospores of Mucor rouxii was compared. The germination process may be divided into two stages: I, spherical growth; II, emergence of a germ tube. In both stages, germination is growth in its strictest sense with overall increases in cell organelles; e.g., the increase in mitochondria is commensurate with the overall increase in protoplasmic mass. Noticeable changes occurring during germination are the disappearance of electron-dense lipoid bodies, formation of a large central vacuole and, most strikingly, formation of a new cell wall. Unlike many other fungi, M. rouxii does not germinate by converting the spore wall into a vegetative wall. Instead, as in other Mucorales, a vegetative wall is formed de novo under the spore wall during germination stage I. This new wall grows out, rupturing the spore wall, to become the germ tube wall. Associated with the apical wall of the germ tube is an apical corpuscle previously described. The vegetative wall exhibits a nonlayered, uniformly microfibrillar appearance in marked distinction to the spore wall which is triple-layered, with two thin electron dense outer layers, and a thick transparent inner stratum. The lack of continuity between the spore and vegetative walls is correlated with marked differences in wall chemistry previously reported. A separate new wall is also formed under the spore wall during anaerobic germination leading to yeast cell formation. On the other hand, in the development of one vegetative cell from another, such as in the formation of hyphae from yeast cells, the cell wall is structurally continuous. This continuity is correlated with a similarity in chemical composition of the cell wall reported earlier.     

COMPARATIVE DEVELOPMENT OF THE RED ALGAL PARASITES BOSTRYCHIOCOLAX AUSTRALIS GEN. ET SP. NOV. AND DAWSONIOCOLAX BOSTRYCHIAE (CHOREOCOLACACEAE,RHODOPHYTA)1

The development of two red algal parasites was examined in laboratory culture. The red algal parasite Bostrychiocolax australis gen. et sp. nov., from Australia, originally misidentified as Dawsoniocolax bostrychiae (Joly et Yamaguishi-Tomita) Joly et Yamaguishi-Tomita, completes its life history in 6 weeks on its host Bostrychia radicans (Montagne) Montagne. Initially the spores divide to form a small lenticular cell, and then a germ tube grows from the opposite pole. Upon contact with the host cuticle, the germ tube penetrates the host cell wall. The tip of the germ tube expands, and the spore cytoplasm moves into this expanded tip. The expanded germ tube tip becomes the first endophytic cell from which a parasite cell is cut off that fuses with a host tier cell. The nuclei of this infected host cell enlarge. As parasite development continues, other host-parasite cell fusions are formed, transferring more parasite nuclei into host cells. The erumpent colorless multicellular parasite develops externally on the host, and reproductive structures are visible within 2 weeks. Tetrasporangia are superficial and cruciately or tetra-hedrally divided. Spermatia are formed in clusters. The carpogonial branches are four-celled, and the carpogonium fuses directly with the auxiliary (support) cell. The mature carposporophyte has a large central fusion cell and sympodially branched gonimoblast filaments. Early stages of development differ markedly in Dawsoniocolax bostrychiae from Brazil. Upon contact with the host, the spore undergoes a nearly equal division, and a germ tube elongates from the more basal of the two spore cells, penetrates the host cell wall, and fuses with a host tier cell. Subsequent development involves enlargement of the original spore body and division to form a multicellular cushion, from which descending rhizoidal filaments form that fuse with underlying host cells. This radically different development is in marked contrast to the final reproductive morphology, which is similar to B. australis and has lead to taxonomic confusion between these two entities. The different spore germination patterns and early germ-ling development of B. australis and D. bostrychiae warrant the formation of a new genus for the Australian parasite.     

Candida albicans mycelial wall structure: supramolecular complexes released by Zymolyase,chitinase and β-mercaptoethanol

Different techniques released from the wall of Candida albicans mycelial cells high molecular weight mannoprotein materials with different levels of complexity. SDS solubilized among others one protein of 180 kDa which reacted with a monoclonal antibody (MAb) specific of a O-glycosylated protein secreted by regenerating mycelial protoplasts [Elorza et al. (1989) Biochem Biophys Res Commun 162:1118–1125]. Zymolyase, chitinase and -mercaptoethanol, released different types of high molecular highly polydisperse mannoprotein materials (>180 kDa) that also reacted with the same MAb. These materials had N-glycosidically linked sugar chains, in addition to the O-glycosidically bonded sugars, as their molecular masses were significantly reduced by Endo H digestion. Besides, the specific materials released by either zymolyase or chitinase seemed to be the same throughout the process of germ tube formation. Transmission electron microscopy of thin sections of cells and walls showed that mannoproteins and chitin are evenly distributed throughout the entire cell wall structure.     

Conidial germination and germ tube elongation of Phomopsis amaranthicola and Microsphaeropsis amaranthi on leaf surfaces of seven Amaranthus species: Implications for biological control

Microsphaeropsis amaranthi and Phomopsis amaranthicola are potential biological control agents for several Amaranthus species. In an effort to understand the initial infection processes with these pathogens, a study was conducted of the conidial germination and germ tube length (μm) on the weed leaf surfaces at 21 °C and 28 °C. Weeds included Amaranthus rudis, A. palmeri, A. powellii, A. retroflexus, A. spinosus, A. hybridus, and A. albus. For P. amaranthicola, conidial germination and germ tube length varied among the seven weed species at both temperatures, while for M. amaranthi the differences in germ tube lengths were significant among weed species only at 21 °C. While the conidia of M. amaranthi and P. amaranthicola germinated on the leaf surfaces of all seven weed species, temperature appeared to impact the number and length of germ tubes on the leaf surfaces. The percentage of germinated conidia and the length of germ tubes at both temperatures were often greater for M. amaranthi than for P. amaranthicola. In order for the fungal pathogen to successfully infect and kill a weedy host, conidia must germinate and form a germ tube, two processes that vary with host species and temperature for M. amaranthi and P. amaranthicola. The extent to which successive infection processes, e.g., penetration, invasion and colonization, contribute to host specificity warrants study.     

Attachment of bean rust cell wall material to host and non-host plant tissue

A preparation of bean rust (Uromyces phaseoli) germ tube walls, consisting of short, filamentous particles, was labeled with fluorescein iso-thiocyanate. Freeze sections of host and non-host tissue were incubated in the labeled preparation. Maximum staining was observed in host plant tissue (Phaseolus vulgaris), in which bean rust regularly forms haustoria. In tissue of the non-host plantsVigna sinensis andPhaseolus lunatus, where fewer haustoria were formed, staining was only weak. However, no staining was observed in the non-host tissue ofPhaseolus aureus, Helianthus annuus, Brassica oleracea andHordeum vulgare in which the infection hypha did not form haustoria. This would appear to indicate that formation of haustoria is induced by a specific attachment of the hyphal wall to the host wall. The possibility that elicitors attach in a similar way, is discussed.Abbreviations FITC Fluorescein iso-thiocyanate - cv cultivar     

The Effect of Gentian Violet on Virulent Properties of <Emphasis Type="Italic">Candida albicans</Emphasis>

The aim of this study was to evaluate the effect of gentian violet (GV) on phospholipase activity, proteinase activity and germ tube formation rate of Candida albicans. Both 12 phospholipase-positive and 12 proteinase-positive C. albicans isolates with Pz values ≤0.89 were obtained. A yeast suspension (1–3 × 10⁷ cfu/ml) of each isolate was prepared. After a brief exposure (60 min) to sub-therapeutic concentrations (0.5 or 2 μg/ml) of GV, Pz value of phospholipase, Pz value of proteinase and germ tube formation rate were determined. Phospholipase activity, proteinase activity and germ tube formation rate in two groups exposed to GV were significantly lower than those in the group unexposed (P < 0.05). The results of this study indicated that sub-therapeutic concentrations of GV may lead to reduction in phospholipase activity, proteinase activity and germ tube formation, and then may suppress virulence and pathogenicity of C. albicans.     

Distinctive tracheid microstructure in stems of Victoria and Euryale (Nymphaeaceae)

Scanning electron microscopy (SEM) photographs of thick sections from liquid‐preserved stems of Victoria cruziana and Euryale ferox show accretions of coarse fibrils on pit membranes of tracheids. The first‐deposited fibrils are randomly orientated; on top of them (facing the tracheid lumina) are axially orientated coarse fibrils. The two systems are interconnected. Axially orientated fibrils were more extensively observed in Euryale than in Victoria and tips of fibrils in Euryale extend over the pit apertures onto secondary wall surfaces. Tracheid–parenchyma interfaces bear rudimentary coarse fibrils on the tracheid side. End walls of Victoria tracheids have highly porose pit membranes, thinner and less complex than those of the lateral intertracheid walls. The structures reported in Victoria and Euryale are consistent with those concurrently reported for stems of other Nymphaeaceae. Although also present in Cabombaceae, the coarse fibrils are otherwise not reported for stems of angiosperms and are not yet reported in roots of any species. Pit membrane remnants in perforation plates of various woody dicotyledons represent a nonhomologous phenomenon. The accretions of coarse fibrils in stem tracheids of Nymphaeaceae do not appear to enhance conduction, although they do contain porosities interconnecting tracheids. Removal of pit membrane remnants from perforation plates of primitive dicotyledon woods by hydrolysis does, on the contrary, suggest conduction enhancement. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 52–57.     

Fine Structure of Germinating Botrytis fabae Sardina Conidia

The fine structure of germinating Botrytis fabae conidia wasstudied using both chemically stained sections and freeze-etchedreplicas. Germinating conidia have fewer organelles than restingconidia, glycogen is absent, and prevacuoles have disappeared.Endoplasmic reticulum which occurs as small strands close tothe cell wall of resting conidia becomes, on germination, multiplesheets surrounding the nuclei. A cross wall is formed at thebase of the germ tube soon after germination commences. Thenew wall material which appears to be continuous with this septalwall is produced, at least partly, from a new wall layer laiddown in the centre of the old conidial wall. An apical corpuscleis present at the apex of young germ tubes. Freeze-etched preparationsshow the formation of lomasomes by the passage of vesicles throughthe plasmalemma of conidia and germ tubes. In young hyphae lomasomescontain a complex arrangement of branching tubules. Some ofthe particles on the outer plasmalemma of young hyphae are arrangedin a geometrical pattern.