The Plum is subject to several diseases of fungal origin.
The organic compounds of the latter are absorbed by the protruding fungal filaments, which take the place of root-hairs, the tree ceasing to develop the latter.
A characteristic feature of the fungal vegetative plantbody (mycelium) is its formation from independent coenocytic tubes or cell-threads.
A solid fungal body may usually be seen to consist of separate hyphae, but in some cases these are so bent and closely interwoven that an appearance like that of ordinary parenchymatous tissue is obtained in section, the structure being called pseudo parenchyrna.
This is especially the case in the lichens (symbiotic organisms composed of a fungal mycelium in association with algal cells), which are usually exposed to very severe fluctuations in external conditions.
Special wound-cork is also often formed round accidental injuries so as to prevent the rotting of the tissues by the soaking in of rain and the entrance of fungal spores and bacteria.
Fungal and phanerogamic parasites can make no use of stich substances as carbon dioxide, but draw elaborated products from the bodies of their hosts.
Since about 1880 our knowledge of the species which can enter into such relationships has been materially extended, and the fungal constituents of the Lichens are known to include Basidiomycetes as well as Ascomycetes.
In the first, which are called ectotropic, the fungal filaments form a thick felt or sheath round the root, either completely enclosing it or leaving the apex free.
The other type is called endctropic. The fungal filaments either penetrate the epidermis of the root, or enter it from the stem and ramify in the interior.
The fungal constituents vary considerably.
That the fixation of the gas is carried out by the fungal organism either in the soil or in the plant, and the nitrogenous substance so produced is absorbed by the organism, which is in turn consumed by the green plant.
The damping off of seedlingsand in saturated soils not only are the roots and root-hairs killed by asphyxiation, but the whole course of soil fermentation is altered, and it takes time to sweeten such by draining, because not only must the noxious bodies be gradually washed out and the lost salts restored, but the balance of suitable bacterial and fungal life must be restored.
Other genera of South American ants - A pterostigma and Cyphomyrmex - make similar fungal cultivations, but they use wood, grain or dung as the substratum instead of leaf fragments.
Each kind of ant is so addicted to its own particular fungal food that it refuses disdainfully, even when hungry, the produce of an alien nest.
The fungal part of the organism nearly always consists of a number of the Discomycetes or Pyrenomycetes, while the algal portion is a member of the Schizophyceae (Cyanophyceae or Blue-green Algae) or of the Green Algae; only in a very few cases is the fungus a member of the Basidiomycetes.
The reproductive organs of the lichen are of a typically fungal character, i.e.
The view of the dual nature of lichens had hitherto been based on analysis; the final proof of this view was now supplied by the actual synthesis of a lichen from fungal and algal constituents.
The majority of the lichens, however, possess a stratified thallus in which the gonidia are found as a definite layer or layers embedded in a pseudoparenchymatous mass of fungal hyphae, i.e.
There are three methods of reproduction of the lichen: by fragmentation, by soredia, by the formation of fungal spores.
Since they are provided with both fungal and algal elements, they are able to develop directly, under suitable conditions, into a new thallus.
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.
We find two chief types of fruit bodies in the lichens, the perithecium and apothecium; the first when the fungal element is a member of the Pyrenomycetes division of the Ascomycetes, the second when the fungus belongs to the Discomycetes division.
The apothecia, though of the normal fungal type and usually disk-shaped, are somewhat more variable, and since the Morphologie and Biologie der Pilze, Mycetozoen und 1 The thalline margin (margo thallinus) is the projecting edge of a special layer of thallus, the amphithecium, round the actual apothecium; the proper margin (margo proprius) is the projecting edge of the apothecium itself.
For some obscure reason the Basidiomycetes do not readily form lichens, so that only a few forms are known in which the fungal element is a member of this family.
Theoretically the lichens may be classified on the basis of their algal constituent, on the basis of their fungal constituent, or they may be classified as if they were homogeneous organisms. The first of these systems is impracticable owing to the absence of algal reproductive organs and the similarity of the algal cells (gonidia) in a large number of different forms. The second system is the most obvious one, since the fungus is the dominant partner and produces reproductive organs.
There are two main divisions of lichens, Ascolichenes and Basidiolichenes, according to the nature of the fungal element, whether an ascomycete or basidiomycete.
The developing seed thus encloses fungal hyphae, which remain dormant within the seed and in spring develop symbiotically with the growth of the wheat plant, doing no apparent injury until the time of fruiting is reached, when the fungus takes complete possession and fills the new seed with a mass of darkcoloured spores.
Professor Seward, however, has found a Zygosporites in situ, terminating an apparently fungal hypha: he suggests a possible comparison with the mould Mucor.