Part I

the entire sporangium is thrown for some distance into the air by a similar contrivance, the basal region of the sporangium having, by the absorption of water, been transformed into a slimy layer which is readily detached. Sphcerobolus, a Gasteromycete, has a small, spherical fruit-body (basidiocarp), the covering of which, when ripe, suddenly bursts, and the basidiospores contained in it are forcibly ejected. The spores which are enclosed in asci are, in some instances, set free from the mother-cell (ascus) prior to their complete development (Elaphomyces, Eurotiuni). In the case of the majority of the Pyrenomycetes and Truffles, the asci swell by the absorption of water into a slimy mass, which gradually disappears, so that the spores lie free in the fruit-body ; they either remain there till the fruit-body decays, as in those which have no aperture (Perisporiaceas, Tuberaceee), or the slimy mass, by its growth, is forced out through the aperture of the sporocarp, taking the spores with it (Nectria). The ejection of the spores by mechanical means takes place in a number of Ascomycetes, and should many spores be simultaneously ejected, a dust-cloud may be seen with the naked eye to arise in the air from the fruit-body. This is the case in the larger species of Peziza, Helvella, Rhytisma, when suddenly exposed to a A damp current of air. distinction is drawn between a simultaneous ejection of all the spores contained in the ascus, and an ejection at FUNGI. 93 intervals (successive), when only one spore at a time is thrown out. The first of these methods is the most frequent, and is brought about by the ascus being lined with a layer of protoplasm, which absorbs water to such a degree that the elastic walls are extended at times to double their original size. The spores are forced up against the free end of the ascus, a circular rupture is made at this point, and the elastic walls contract, so that the fluid with the spores is ejected. Special means may in some instances be found to keep the spores together, and compel their simultaneous ejection. Thus, a tough slime may surround all the spores (Saccobolus}, or a chain- apparatus, similarly formed of tough slime; or there may be a hooked appendage from each end of the spores which hooks into the appendage of the next spore (Sordaria). The paraphyses occurring between the asci in many Ascomycetes, also play a part in the distribution of the spores, by reason of the pressure they exercise. The asci in some of the Pyrenomycetes, which are provided with jar-shaped fruit-bodies, elongate to such an extent that, without becoming detached from their bases, they reach the mouth of the fruit-body one at a time, burst and disperse their spores, and so make room for those succeeding. An ejection of the spores at intervals from the ascus is rarer. It takes place, for instance, in Pleospora, whose asci have a double wall. The external wall, by absorption of water, at last becomes ruptured, and the internal and more elastic membrane forces itself out in the course of a few seconds to one of two or three times greater length and thickness, so that one spore after another is forcibly ejected from a narrow aperture at the end of the ascus. Germination of spores (conidia and chlamydospores). In many spores may be found one or more germ-pores, i.e. thinner places, either in the inner membrane (uredospores. Sordaria) or in the external membrane (teleutospores in Rust-Fungi), through which the germination takes place. Generally this does not occur till the spores have been set free : in some Ascomycetes germination commences inside the ascus (Taphrina, Sclerotinia) . The different ways in which the spores germinate maybe classified into three groups. I. THE ORDINARY GERMINATION occurs by the spore emitting a germ-tube, which immediately developes into a mycelium. In spores with a double wall it is only the inner membrane which forms the germ-tube. In swarmspores a single wall is formed after the withdrawal of the cilia, and this, by direct elongation, 94 FUNGI. becomes the germ-tube. The protoplasm accumulated in the spore enters the hypha, which, in pure water, can only grow as long as the reserve nourishment lasts. 2. GERMINATION WITH PROMYCELIUM differs only by the circum- stance that the hypha developed from the germ-tube has a Tery limited growth, and hence it does not immediately develope into a mycelium, but produces conidia (Rust- and Brand-Fungi). This promycelium must only be regarded as an advanced development of a conidiophore or basidium. 3. THE YEAST-FORMATION of conidia consists in the production of outgrowths, very much constricted at their bases, from one or more places. Each of the conidia formed in this manner may again germinate in the same way. When sufficient nourishment is present, a branched chain of such conidia is formed, and these are iiiially detached from one another. Yeast-like buddings from the conidia are produced in various Fungi, e.g. Ascoidea, Protomyces, Ustilaginece, Ascomycetes, Tremellacese, etc. In the Ustilaginese these conidia are an important element in the development. The budding conidia of Exobasidium forms a " mould " on the nutritive solution. The yeast-like conidia are not to be con- founded with the " " Mucor-yeast (comp. Mucoraceae). For Sac- charomijces see Appendix to the Fungi, page 176. In a compound spore (i.e. when a mass of spores are associated together) each spore germinates on its own account. There are sometimes, however, certain among them which do not germinate, but yield their contents to those which do. The length of time for which conidia can retain their power of germination is shortest (being only a few weeks) in those having thin walls and containing a large supply of water (Peronosporaceae, Uredinaceae). In many spores a resting period is absolutely neces- sary before they are able to germinate (resting spores). It has been observed in some spores and conidia, that the faculty of germinating may be preserved for several years if the conditions necessary for germination remain absent (Ustilagineae, Eurotium, Penicillium). The optimum, minimum and maximum temperatures required for the germination of the spores has been decided in the case of a good many Fungi. A large portion of the most common Fungi have their optimum at 20C., minimum at 1-2C, maximum at 40C. In the case of pathogenic Fungi the optimum is adapted to the temperature of the blood. Fungi living in manure, whoso ZYGOMICETES. 95 spores are often adapted to germinate in the alimentary canals of warm-blooded animals, have an optimum corresponding to the temperature of these animals, but with a little margin. Systematic Division. The lowest class of the Fungi is that of the PHYCOMYCETES, which have an unicellular mycelium, sexual and asexual reproduction, and have doubtless sprung from sporangia-bearing, lower Green Algse. From the Phycomycetes (and certainly from the Zygomycetes) spring two well defined branches, each with numerous distinct species; to the one branch belong the HEMIASCI and the ASCOMYCETES, to the other the HEMIBASIDII and the BASIDIOMYCETES. Ascomycetes and Basidiomycetes may be united under the title of MYCOMYCETES or HIGHER FUNGI. The Hemiasci and the Hemibasidii constitute the class of MESOMYCETES. The Hemiasci are an intermediate form between Zygomycetes and Ascomycetes ; the Hemibasidii a similar group between the Zygomycetes and Basidiomycetes. Mesomycetes and Mycomycetes have only asexual reproduction ; sexual reproduction is wanting. Their mycelium is multicellular. Up to the present time about 39,000 species have been described. Review of the divisions of the Fungi : class L Phycomycetes (Algal-Fungi). Sub-Class 1. Zygomycetes. Sub-Class 2. Oomycetes. Family 1. ENTOMOPHTHORALES. Family 2. CHYTRIDIALES. Family 3. MYCOSIPHONALES. class ii. Mesomycetes. Sub-Class 1. Hemiasci. Sub-Class 2. Hemibasidii (Brand-Fungi). Class in. Mycomycetes (Higher Fungi). Sub-Class i. Ascomycetes. Series 1. Exoasci. Series 2. Carpoasci. Family 1. GYMNOASCALES. -\ Family 2. PERISPORIALES. Angiocarpic Exoasci. Family 3. PYRENOMYCETES. J FamilyJ 4. HYSTERIALES. 1 \ TT Herm-angiocarpic Exoasci. Family 5. DISCOMYCETES. ) Family 6. HELVELLALES. Gymnocarpic (?) Exoasci. Additional : ASCOLICHENES. Lichen-forming Ascomycetes. W.B. H 96 ZYGOMYCETES. Sub-Class 2. Basidiomycetes. Series 1. Protobasidiomycetes. Partly gymnocarpic, partly angiocarpic. Series 2. Autobasidiomycetes. Family 1. DACRYOMYCETES. Gymnocarpic. Family 2. HYMENOMYCETES. Partly gymnocarpic, partly hemi- angiocarpic. Family 3. PHALLOIDEJE. Hemiangiocarpic. Family 4. GASTEROMYCETES. Angiocarpic. Additional : BASIDIOLICHENES. Lichen-forming Basidiomycetes. Additional to the Fungi : FUNGI IMPEBFECTI. Incompletely known (Saccliaromyces, Oidium-iorms, etc.). Class 1. Phycomycetes 1 (Algal-Fungi). This group resembles Vaucheria and the other Siphonese among the Alg83. ORGANS OF NUTRITION. The mycelium is formed of a single cell, often thread-like and abundantly branched (Fig. 78). Vegetative propagation by chlamydospores and oidia. Asexual reproduction by endospores (sometimes swarmspores) and conidia. Sexual reproduction by conjugation of two hyphae as in the Conjugate, or by fertilisation of an egg-cell in an oogonium. On this account the class of the Phycomycetes is divided into two sub-classes : ZYGOMYCETES and OOMYCETES. Sub-Class I. Zygomycetes. Sexual reproduction takes place by zygospores, which function as resting-spores, and arise in consequence of conjugation (Fig. 81); in the majority of species these are rarely found, and only under special conditions. The most common method of reproduction is by endospores, by acrogenous conidia, by chlamydospores, or by oidia. Swarmspores are wanting. Parasites and saprophytes (order 6 and 7). The zygospores are generally produced when the formation of sporangia has ceased; e.g. by the suppression of the sporangialhyphce (Mucor mucedo}, or by the diminution of oxygen; Pilobolus cnjstallinus forms zygospores, when the sporangia are infected with saprophytic Piptocephalis or Pleotrachelus. A. Asexual reproduction only by sporangia. Order 1. Mucoraceae. The spherical sporangia contain many spores. The zygospore is formed between two unicellular branches (gametes). 1 Also termed Water-Fungi (Wasserpilzen). ZYGOMYCETES. 97 The unicellular mycelium (Fig. 78) of the Mucoraceae branches abundantly, and lives, generally, as a saprophyte on all sorts of dead organic remains. Some of these Fungi are known to be cap- able of producing alcoholic fermentation, in common with the Sac- charomyces. This applies especially to Chlamydomucor racemosus (Mucor racemosus}, when grown in a saccharine solution, and deprived of oxygen; the mycelium, under sucli conditions, becomes divided by transverse walls into a large number of small cells. FIG. 78. Mucormucedo. A mycelium which has sprung from one spore, -whose position is marked by the * : a, b, c are three sporangia in different stages of development ; a is the youngest one, as yet only a short, thick, erect branch ; b is commencing to form a sporangium which is larger in c, but not yet separated from its stalk. Many of these swell out into spherical or club-shaped cells, and when detached from one another become chlamydospores, which abstrict new cells of similar nature (Fig. 79). These chlamydo- spores were formerly erroneously termed " mucor-yeast," but they must not be confounded with the yeast-conidia (page 94). They are shortened hyphae, and are not conidia of definite size, shape, and point of budding. Oidia are also found in Chlamydomucor. 98 ZYGOMYCETES. , The Mucoracese, in addition to the chlamydospores and oidia, have a more normal and ordinary method of reproduction; viz. r by spores which are formed without any sexual act. Mucor has- round sporangia ; from the mycelium one or more long branches,, sometimes several centimetres in length, grow vertically into the air ; the apex swells (Figs. 78, 80) into a sphere which soon becomes separated from its stalk by a transverse wall ; in the interior of this sphere (spor- angium) a number1 of spores are formed which eventually are set free by the rupture of the wall. The transverse wall protrudes into the sporangium and forms the well-known columella (Fig. 80 d, e). The formation of PIG. 79. Chlamydospores of CTiZamydo* mucor racemosus ( x 375 times.) spores takes place in various ways among the different genera. SEXUAL EEPEODUCTION by conjugation takes place in the following manner. The ends of two hyphte meet (Fig. 81) and become more or less club-shaped ; the ends of each of these are cut off by a cell- wall, and two new small cells (Fig. 81 A) are thus .formed, these coalesce and give rise to a new cell which becomes the very thick- walled zygote (zygospore), and germinates after a FIG. 80. JJfitcor mucedo : a a spore commencing to germinate ( x 300 times); b a germi- nating spore which has formed a germ-tube from each end ( x 300 times) ; c the apex of a young sporangium before the formation of spores has commenced; the stalk is protruded in the sp orangium in the form of a column : on the wall of the sporangium is found a very fine incrustation of lime in the form of thorn-like projections ; d a sporangium in which the formation of spores has commenced ; e a sporangium, the wall of which is ruptured,, A leaving a remnant attached to the base of the columella as a small collar. few spores are- seen still adhering to the columella. ZYGOMYCETES. 99 period of rest, producing a new hypha, which bears a sporangium (Fig. 81 JS). Mucor mucedo, Pin- mould, resembles some- what in appearance Penicillium crustaceum and is found growing upon various organic materials (bread, jam, dung, etc.). Pilobolus (Figs. 83, 84) grows on manure. Its sporangium (Fig. 84 a") is formed during the night and by a peculiar mechanism (page 92) is shot away from the plant in the course of the day. This generally takes place in the summer, between eight and ten a.m. The sporangium is shot away to a height which may be 300 times greater than that of the plant itself, and by its stickiness it becomes attached to portions of plants, etc., which are in the vicinity. If these are eaten by animals, the spores pass into the alimentary canal and are later on, sometimes even in a germinating condition, passed out with the excrement, in which they form new mycelia. Phycomyces nitens (" Oil-mould ") is the FIGS. 81, 82. afucor mucedo: A-C stapes in the formation of the zygote ; D zygote ; E germination of zygote : the exospore has burst, and the endospore grown into a bypha bearing a sporangium. largest of the Mould Fungi ; its sporangiophores may attain the height of 10-30 c. m. Order 2. Rhizopaceae. Ehizopus nigricans (Mucor stolonifer) which lives on decaying fruits containing sugar, on bread, etc., has, at the base of the sporangiophores, tufts of rhizoids, i e. hyphae, which function as organs of attachment. From these, " runners " are produced which in a similar manner develope sporangiophores and rhizoids. Order 3. Thamnidiaceae. On the same sporangiophore, in addition to a 100 OOMYCETES. large, terminal, many-spored sporangium, many smaller, lateral sporangia are formed with a few spores. Thamnidium. B. Asexual reproduction by sporangia and conidia. Order 4. Choanephoraceae. Choanephora with creeping endophytic mycelium, and perpendicular sporangiophores. Order 5. Mortierellaceae. Mortierella polycephala produces on the same mycelium conidia and sporangiophores. M. rostafinskii has a long stalked sporangiophore, which is surrounded at its base by a covering of numerous felted hyphae. FIG. 83. PiZobolus. Mycelium (a, a), with a sporangiophore (A) and the fundament of another ( B). FIG. 81. Pilololus. Sporangium (a") with stalk (a-c), which is covered by many small drops of water pressed out by tur- gescence. C. Asexual reproduction only by conidia. Order 6. Chsetocladiacese. The conidia are abstricted singly and aerogenously. Chcetocladium is a parasite on the larger Mucoraceas. Order 7. Piptocephalidacese. The conidia are formed acrogenously and in a series, by transverse divisions. The zygospore arises at the summit of the conjugating hyphse, which are curved so as to resemble a pair of tongs. 'Piptocephalis and Syncephalis live parasitically on the larger Mucorace. Sub-Class 2. Oomycetes. Sexual reproduction is oogamous with the formation of brown, thick-walled oospores which germinate after a period of rest. Asexual reproduction by conidia and swarmspores. Parasites, seldom saprophytes. The oospores are large spores which are formed from the egg- A cell (oosphere) of the oogonium (oosporangium, Fig. 89, 95). branch of the mycelium attaches itself to the oogonium and forms at its apex the so-called " antheridium " 1 (pollinodium ) : this sends one or more slender prolongations (fertilising tubes) through the wall of the oogonium to the egg-cell. 1 Antheridium is preferred in this sub-class as keeping amore uniform term (Kn). OOMYCETES. 101 A fertilisation, a passage of the contents of the antheridium to the egg-cell, has as yet only been observed in Pythium; in Phytophthora only one small mass of protoplasm passes through the fertilising tube to the egg-cell; in Pero- A FIG. 85. Empusn muscce (Fly-mould). I. fly killed by the fungus, surrounded by a white layer of conidia. II. The conidiophores (t) projecting from the body of the fly. Some of the conidia, a few of which have developed secondary conidia, are attached to the hairs A A (mag. 80 times). III. perfect hypha. IV. hypha in the act of ejecting a conidinm A (c), enveloped in a sticky slime (g). V. conidium which has developed a secondary conidium(sc). VI. A branched hypha produced by cultivation. VII. A secondary con- idium which has produced a small mycelium (m). VIII. A conidinm germinating on the fly's body. IX. Mycelium. X. Conidia germinating like yeast in the fatty tissue of the vm. fly. (III.-VII. and IX. magnifled 300 times ; and X. magnified 500 times.) 102 OOMYCETES. nospora and the Saprolegniaceae'no protoplasm can be observed to pass through the fertilising tube, so that in these instances parthenogenesis takes place ; Saprolegnia thuretii, etc., have generally even no antheridia, but nevertheless form normal oospores. Fertilisation of the egg-cell by means of self-motile spermatozoids is only found in Monoblepharis sphcerica. A. Asexual reproduction by conidia only. Family 1. Entomophthorales. The mycelium is richly branched. The family is a transitional step to the conidia-bearing Zygomycetes, since the oospores of many members of this family arise, and are formed, like zygospores. Order 1. Entomophthoraceae. Mycelium abundantly developed. This most frequently lives parasitically in living insects, causing their death. The conidiophores forming the conidiallayer project from the skin, and abstrict a proportionately large conidium which is ejected with considerable force, and by this means transferred to other insects. These become infected by the entrance of the germ-tube into their bodies. The spherical, brown resting-spores develope inside the bodies of insects and germinate by emitting a germ- tube. GENERA : Empusa has a good many species which are parasitic on flies, moths, grasshoppers, plant-lice. The conidia emit a germ-tube which pierces the skin of the insect ; a number of secondary conidia are then produced inside its body, by division or by gemmation similar to that taking place in yeast, each of which grows and becomes a long unbranched hypha, and these eventually fill up the body of the animal, causing distension and death. Each of these hyphae projects through the skin, and abstricts a conidium, which is ejected by a squirting contrivance. The best known species is E. muscce (Fig. 85), which makes its appearance epidemically towards autumn on the common house-fly, and shows itself by the dead flies which are found on the windows and walls attached by their probosces, distended wings, and legs. They have swollen abdomen, broad white belts of hyphse between the abdominal rings, and are surrounded by a circle of whitish dust formed by the ejected conidia. Entomophthora sends out, at definite places, from the mycelium hidden in the insect's body, bundles of hyphae, which serve the purpose of holding fast the dead insects, the ramifications attaching themselves to the substratum : the conidiophores are branched, the conidia are ejected by the divisional walls between the hyphaa and the conidia dividing into two layers, those which terminate the hyphae suddenly expanding and throwing the conidia into the air. E. radicans makes its appearance epidemically on caterpillars. B. Asexual reproduction by zoospores or conidia. Family 2. Chytridiales. In this family the mycelium is very sparsely developed or is wanting. The entire plant consists principally or entirely of a OOMYCETES. 103 single zoosporangium whose zoospores have generally one cilium. The resting-spores arise either directly from the zoosporangium, which, instead of forming zoospores, surrounds itself by a thick cell-wall ; or they are formed by the conjugation of two cells (in which case they are spoken of as oospores). Microscopic Fungi, parasitic on water plants (especially Algee) or small aquatic ani- mals, seldom on land plants. Order 1. Olpidiaceae. and resting-spores. Without mycelium. Swarmspores In the Olpidiez, the swarmspores, probably, most frequently form themselves into a plasmodium (naked mass of protoplasm) which may become a single zoosporangium or a resting sporangium. Olpidium trifolii occurs in Trifolium repens. In the Synchytriece the plasmodium emerging from the swarmspores breaks up either at once, or after a period of rest, into smaller plasmodia, each of which will become a zoosporangium. Synchytrium anemones is found on Anemone nemorosa ; S. mercurialis on Mercurialis perennis ; S. aureum on many plants, particularly Lysintachia nunimularia. FIG. 86. Chytridium lagenula. Zoosporangium a before, b after the liberation of the swarmspores. FIG. 87. Obelidium mucronatum : m mycelium ; s swarmspores. Order 2. Rhizidiaceae. Mycelium present. Zoospores and resting-spores. Chytridium (Fig. 86). Obelidium (Fig. 87) is bicellular ; the one cell is the mycelium, the other the zoosporangium ; found on insects. The species of Cladochytriiim, are intercellular parasites on marsh plants. Physoderma. Order 3. Zygochytriacese. Mycelium present. Zoospores and oospores. The latter are the product of the conjugation of two cells (Fig. 88). Polyphagus euglence on Euglena viridis. Uroplilyctis pulposa on species of Chenopodinm. (Edomyces leproides on the Beet-rooc. 104 OOMYCETES. Family 3. Mycosiphonales. The mycelium is bladder-like or branched. Zoospores. Sexual reproduction by oospores, which are produced in oogonia. The latter are fertilised, in some forms, by the antheridium. Order 1. Ancylistacese. The entire bladder-like mycelium is used for the construction of zoosporangia, oogonia, or antheridia. Lagenedium is parasitic on Spirogyra, etc. Order 2. Peronosporaceae. Almost entirely parasites. The unicellular, often very long and abundantly branched mycelium lives in the intercellular spaces of living plants, especially in the green portions, and these are more or less destroyed and deformed in consequence. Special small branches (suction-organs, m B FIG. 88. Polyphagus euglence. A with smooth, with thorny oospores ; and /the two conjugating cells. " haustoria ") are pushed into the cells in order to abstract nourishment from them. Both oospores and conidia germinate either immediately, or they develope into sporangia with swarm- spores, having always two cilia. Only one oospore is formed in each oogonium ; its contents (Fig. 89) divide into a centrally placed egg-cell and the " periplasm " surrounding it; this is of a paler colour and on the maturity of the oospore forms its thick, brown, external covering. The Potato-fungus (Phytophthora infestans) is of great interest. Its thallus winters in the Potato-tuber; other organs for pass- ing the winter, such as oospores, are not known. When the tuber germinates, the Fungus-hyphse penetrate the young shoot and keep pace with the aerial growth and development of the plant. The conidiophores emerge through the stomata, especially on the under side of the leaves ; they branch like a tree (Fig. 90), and OOMYCETES. 105 appear to the naked eye as a fine mould on the surface of the plant. The disease soon makes itself known by the brown colouring of those parts of the plant which are attacked, and by their withering. An ovoid conidium arises at first by the formation of a dividing- wall at the apex of each branch of the conidiophore My FIG. 89. Peronospora. aJsiiiearutn. celiam with egg-cell and antheridium. infestans (strongly magnified). Cross section through a small rtion of a Potato-leaf (the under side turned upwards) : a the mycelium ; b b two conidiohores projecting through a stoma; c conidia; e the spongy tissue of the leaf; g the pifiannis. 106 OOMYCETES. (Fig. 90 c c), and immediately underneath it another is formed, which pushes the first to one side, and so on. These conidia sometimes germinate

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