Group of spore-cases (sorus) on back of leaf (X 4).
The spore cell gives rise to a " sporelarva," which is set free in the coelenteron and grows into a medusa.
The parasite effects a lodgment in the host either by invading it as a free-swimming planula, or, apparently, in other cases, as a spore-embryo which is captured and swallowed as food by the host.
Frequently, also, a considerable differentiation of vegetative tissue occurs in the wall of the spore-capsule itself, and in some of the higher forms a special assimilating and transpiring organ situated just below the capsule at the top of the seta, with a richly lacunar chlorophyllous parenchyma and stomata like those of the wall of the capsule in the Anthocerotean liverworts.
The gametophyte, which bears the sexual organs, is either a free-living thallus corresponding in degree of differentiation with the lower liverworts, or it is a mass of cells which always remains enclosed in a spore and is parasitic upon the sporophyte.
In the vascular cryptogams and phanerogams it takes place in the spore mother cells and the reduced number is found in all the cells of the gametophyte, the full number in those of the sporophyte.
A division by fission followed by Endogenous spore formation, characteristic of the Schizosaccharomycetes.
The two divisions of the spore mother cell in which the reduction takes place, follow each other very rapidly and are known as Heterotype and Homotype (Flemming), or according to the terminology of Farmer and Moore (1905) as the meiotic phase.
On the under side of the leaf these patches are white and are composed of the spore-bearing hyphae.
Previously to Hansen's work the only way of differentiating I Hansen found there were three species of spore-bearing Saccharomycetes and that these could be subdivided into varieties.
The sporogonium of the liverworts is in the simpler forms simply a spore-capstile with arrangements for the development, protection and distribution of the spores.
Thus, in a phanerogam, the sepals, petals, stamens and foliage-leaves all come under the category leaf, though some are parts of the perianth, others are spore-bearing organs (sporophylls), and others carry on nutritive processes.
Ascophorous, producing asci; ascospore, the spore (or sporule) developed in the ascus; ascogonium, the organ producing it, &c.
Sterilization then becomes an easier task, the milk drawn under these conditions being very poor in spore-forming bacteria.
The soredia are the most successful method of reproduction in lichens, for not only are some forms nearly always without spore-formation and in others the spores laregly abortive, but in all cases the spore represents only the fungal component of the thallus, and its success in the development of a new lichen-thallus depends on the chance meeting, at the time of germination, with the appropriate algal component.
Sometimes the two cavities are restricted to the two ends of the spore, the polaribilocular type and the two loculi may be united From Beitrcge zur Wissenschaftlichen Botanik.
Spore of Physica parietina.
Delage has distinguished as multiplication those cases in which the new individual arises from a mass of cells which remain a part of the maternal tissues during differentiation, reserving the term reproduction for those cases in which the spore or cell which is the starting-point of the new individual begins by separating from the maternal tissues; but the distinction is inconvenient in practice and does not appear to carry with it any fundamental biological significance.
Physiologically, any cell or group of cells separated off from a hypha or unicellular fungus, and capable of itself growing out - germinating - to reproduce the fungus, is a spore; but it is evident that so wide a definition does not exclude the ordinary vegetative cells of sprouting fungi, such as yeasts, or small sclerotium like cell-aggregates of forms like Coniothecium.
Whether a spore results from the sexual union of two similar gametes (zygospore) or from the fertilization of an egg-cell by the protoplasm of a male organ (oospore); or is developed asexually as a motile (zoospore) or a quiescent body cut off from a hypha (conidium) or developed along its course (oidium or chlamydospore), or in its protoplasm (endospore), are matters of importance which have their uses in the classification and terminology of spores, though in many respects they are largely of academic interest.
The term "receptacle" sometimes applied to these spore-bearing _ hyphae is better replaced by sporophore.
The sporophore is obsolete when the spore-bearing hyphae are not sharply distinct from the mycelium, simple when the constituent hyphae are isolated, and compound when the latter are conjoined.
The chief distinctive characters of the sporogenous hyphae are their orientation, usually vertical; their limited apical growth; their peculiar branching, form, colour, contents, consistency; and their spore-production.
According to the characters of the last, we might theoretically divide them into conidiophores, sporangiophores, gametophores, oidiophores, &c.; but since the two latter rarely occur, and more than one kind of spore or spore-case may occur on a sporophore, it is impossible to carry such a scheme fully into practice.
Bary.) (X 400.) undergoes segmentation into more or less numerous globular masses, each of which secretes an enveloping cell-wall and becomes a spore (endospore), and branched systems of sporangia may arise as before (Thamnidium).
Compound sporophores arise when any of the branched or unbranched types of spore-bearing hyphae described above ascend into the air in consort, and are more or less crowded into definite layers, cushions, columns or other complex masses.
Gelatinous or mucilaginous degenerations of cell-walls are frequently employed in the interests of spore dispersal.
The mucilage surrounding endospores of Mucor, conidia of Empusa, &c., serves to gum the spore to animals.
They are characterized especially by the zygospores, but the asexual organs (sporangia) exhibit interesting series of changes, beginning with the typical sporangium of Mucor containing numerous endospores, passing to cases where, as in Thamnidium, these are accompanied with more numerous small sporangia (sporangioles) containing few spores, and thence to Chaetocladium and Piptocephalis, where the sporangioles form but one spore and fall and germinate as a whole; that is to say, the monosporous sporangium has become a conidium, and Brefeld regarded these and similar series of changes as explaining the relation of ascus to conidium in higher fungi.
According to his view, the ascus is in effect the sporangium with several spores, the conidium the sporangiole with but one spore, and that not loose but fused with the sporangiole wall.
These structures cannot 3, then be produced from the product of a single spore nor even from the thalli derived from any two spores.
These disjunctors serve as points of application for the elastic push of the swelling spore-ends, and as the connecting outer lamella of cell-wall suddenly gives way, the spores are jerked asunder.
- MOSt of the recent work of importance in this group deals with the cytology of sexual reproduction and of spore-formation, and the effect of external conditions on the production of reproductive organs.
In some cases nuclear division is carried further before spore-formation occurs, and the number of spores is then 16, 32 and 64, &c.; in a few cases the number of spores is less than eight by abortion of some of the eight nuclei.
The characters employed by experts for determining a species of yeast are the sum of its peculiarities as regards form and size: the shapes, colours, consistency, &c., of the colonies grown on certain definite media; the optimum temperature for spore-formation, and for the development of the "veils"; and the behaviour as regards the various sugars.
It was formerly the custom to include with the Fungi the Schizomycetes or Bacteria, and the Myxomycetes or Mycetozoa; but the peculiar mode of growth and division, the cilia, spores and other peculiarities of the former, and the emission of naked amoeboid masses of protoplasm, which creep and fuse to streaming plasmodia, with special modes of nutrition and spore-formation of the latter, have led to their separation as groups of organisms independent of the true Fungi.
At other times the spores are divided by both transverse and longitudinal septa producing the muriform (murali-divided) spore so called from the resemblance of the individual chambers to the stones in a wall.
The growth of lichens is extremely slow and many of them take years before they arrive at a spore-bearing stage.
The spore-cell multiplies by division, while the enveloping cell is nutrient and protective.