In some of the true Ascomycetes, such as Penicillium glaucum, the conidia if grown in saccharine solutions, which they have the power of fermenting, develop single cell yeast-like forms, and do not - at any rate for a time - produce again the characteristic branching mycelium.
Bees carry the spores of Scierotinia as they do the pollen of the bilberries, and flies convey the conidia of ergot from grain to grain.
Cell budding takes place in yeast and in the formation of the conidia of Fungi.
The fungus mycelium grows between the cuticle and the epidermis, the former being ultimately ruptured by numerous short branches bearing spores (conidia) by means of which the disease is spread.
Pear trees may 2, Section of leaf surface showing the also be attacked by a great spores or conidia, c, borne on long variety of insect pests.
Portion of the mycelium of the fungus bearing spores (conidia), s, on erect branches, X250.
This disease has been successfully treated with a spray of copper sulphate and lime, or sulphate of iron; solutions of these salts prevent the conidia from germinating.
Bornet describes free conidia in Arnoldia minitula, and Placodium decipiens and Conidia-formation has been described by Neubner in the Caliciae.
In one view they are mere asexual conidia, and the term pycnoconidia is accordingly applied since they are borne in structures like the non-sexual pycnidia of other fungi.
Forms of which we only know certain stages, such as conidia, pycnidia, &c., and which there are reasons for regarding as merely the corresponding stages of higher forms. Saccardo also included about 400 species of Myxomycetes and 650 of Schizomycetes.
More generally the hypha below the septum grows forwards again, and repeats this process several times before the terminal conidium falls, and so a chain of conidia results, the oldest of which terminates the series (Erysiphe); when the primary branch has thus formed a basipetal series, branches may arise from below and again repeat this process, thus forming a tuft (Penicillium).
Or the primary hypha y first swell at its apex, and put forth a series of short peg-like branches (sterigmata) from the increased surface thus provided, each of which develops a similar basipetal chain of conidia (Aspergillus), and various combinations of these processes result in the development of numerous varieties of exquisitely branched sporophores of this type (Botrytis, Botryosporium, Verticillium, &c.).
A second type is developed as follows: the primary hypha forms a septum below its apex as before, and the terminal conidium, thus abstricted, puts out a branch at its apex, which starts as a mere point and rapidly swells to a second conidium; this repeats the process, and so on, so that we now have a chain of conidia developed in acropetal succession, the oldest being below, and, as in Penicillium, &c., branches put forth lower down may repeat the process (Hormodendron).
The simple sporophore does not necessarily terminate in conidia, however.
The same laws apply to the individual hyphae and their branches as to simple sporophores, and as long as the conidia, sporangia, gametes, &c., are borne on their external surfaces, it is quite consistent to speak of these as compound sporophores, &c., in the sense described, however complex they may become.
In the simplest case the stroma, after bearing its crop of conidia or oidia, develops ascogenous branches in the loosened meshes of its interior (e.g.
- Ordinary conidia and similarly abstricted dry spores are so minute, light and numerous that their dispersal is ensured by any current of air or water, and we also know that rats and other burrowing animals often carry them on their fur; similarly with birds, insects, slugs, worms, &c., on claws, feathers, proboscides, &c., or merely adherent to the slimy body.
The mucilage surrounding endospores of Mucor, conidia of Empusa, &c., serves to gum the spore to animals.
In many cases the slimy masses of spermatia (Uredineae), conidia (Claviceps), basidiospores (Phallus, Coprinus), &c., emit more or less powerful odours, which attract flies or other insects, and it has been shown that bees carry the flagrant oidia of Sclerotinia to the stigma of Vaccinium and infect it, and that flies carry away the foetid spores of Phallus, just as pollen is dispersed by such insects.
Sexual reproduction as above, asexual by sporangia or conidia or both: Mucoraceae.
Conidia (basidiospores) borne in fours on a special conidiophore, the basidium.
When the free ends of the hyphae emerge again into the air they swell up into spherical bodies which may either fall off and behave as conidia, each putting out a germ-tube and infecting the host; or the germ-tube itself swells up into a zoosporangium which develops a number of zoospores.
The development of the "conidia" as true conidial spores or as zoosporangia may occur in one and the same species (Cystopus candidus, Phytophthora infestans) as in Pythium described above; in other cases the direct conidial germination is characteristic of genera - e.g.
Plasmopara, &c. In Cystopus (Albugo) the "conidia" are abstricted in basipetal chain-like series from the ends of hyphae which come to the surface in tufts and break through the epidermis as white pustules.
The classification of the Mucorini depends on the prevalence and characters of the conidia, and of the sporangia and zygospores - e.g.
In these three genera the conidia are cast off with a jerk somewhat in the same way as the sporangium of Pilobolus.
The discovery of the yeast-conidia of these fungi, and their thorough investigation by Brefeld, have thrown new lights on the group, as also have the results elucidating the nature of the ordinary dark spores - smuts, bunt, &c. - which by their mode of origin and development are chlamydospores.
Brefeld regarded the promycelium as a kind of basidium, bearing lateral or terminal conidia (comparable to basidiospores), but since the number of basidiospores is not fixed, and the basidium has not yet assumed very definite morphological characters, Brefeld termed the group Hemibasidii, and regarded them as a halfway stage in the evolution of the true Basidiomycetes from Ph co Y Y mycetes, the Tilletia type leading to the true basidium (Autobasidium), the Ustilago type to the proto pm basidium, with lateral spores; but this p m view is based on very poor evidence, so that it is best to place these forms?p, c;,::, as a separate group, the Ustilaginales.
The yeast-conidia, which bud off from the conidia or their resulting mycelium when sown in nutrient solutions, are developed in successive crops by budding exactly as in the yeast plant, but they cannot ferment sugar solutions.
It is the rapid spread of these yeast-conidia in manure and soil waters which makes it so difficult to get rid of smuts, &c., in the fields, and they, like the ordinary conidia, readily infect the seedling wheat, oats, barley or other cereals.
When the flowers form, however, the mycelium sends hyphae into the young ovaries and rapidly replaces the stores of sugar and starch, &c., which would have gone to make the grain, by the soot-like mass of spores so well known as smut, &c. These spores adhere to the grain, and unless destroyed, by "steeping" or other treatment, are sown with it, and again produce sporidia and yeast-conidia which infect the seedlings.
Four ripe asci, a i, a2, with eight spores, a 3, a4, with yeast-like conidia abstricted from the spores.
Besides peritheca the members of the Erysiphaceae possess conidia borne in simple chains.
They have characteristic conidiophores bearing numerous conidia, and also cleistothecia which are spherical in form and yellowish in colour.
The conidia are fragrant and are carried by bees to the stigma of the bilberry; here they germinate with the pollen and the hyphae pass with the pollen tubes down the style; the former infect the ovules and produce sclerotia, therein reducing the fruits to a mummified condition.
Heteroica, is heteroecious; the ascospores infecting the leaves of Vaccinium uliginosum, while the conidia which then arise infect only Ledum palustre.
They have never been found to cause in fection, and they have not the characters of conidia; the large size of their nuclei, the reduction of their cytoplasm and the absence of reserve material and their thin cell wall all point to their being male gametes.
Just as the uredospores and aecidiospores both show these specialized characters in the case of Puccinia graminis so we find that both the conidia and ascospores of E.
If, however, conidia from B.
Hordaceus, the conidia which develop on that plant are now able to infect B.
Salmon also found that injury of a leaf by mechanical means, by heat, by anaesthetics, &c., would affect the immunity of the plant and allow infection by conidia which was not able to enter a normal leaf.