_String-like_ mycelia may be found, for example, in _Phallus_, _Coprinus_, and are formed of hyphæ, which run more or less parallel to each other. _Membrane-like_ mycelia are chiefly to be found in Fungi growing on tree-stems (Polyporaceæ and Agaricaceæ); they may have a thickness varying from that of the finest tissue-paper to that of thick leather, and may extend for several feet. The peculiar horny or leather-like strands and plates which, for instance, appear in _Armillaria mellea_, are known as _Rhizomorpha_; they may attain a length of more than fifty feet. The _tuber-like_ mycelia or _sclerotia_ play the part of resting mycelia, since a store of nourishment is accumulated in them, and after a period of rest they develope organs of reproduction. The sclerotia are hard, spherical, or irregular bodies, from the size of a cabbage seed to that of a hand, internally white or greyish, with a brown or black, pseudo-parenchymatous, external layer. Sclerotia only occur in the higher Fungi, and are found both in saprophytes, _e.g. Coprinus_, and in parasites, _e.g. Claviceps_ (Ergot), _Sclerotinia_. =Reproduction.= SEXUAL REPRODUCTION is found only among the lower Fungi which stand near to the Algæ, the Algal-Fungi, and takes place by the same two methods as in the Algæ, namely by _conjugation_ and by the _fertilisation_ of the egg-cell in the oogonium. The majority of Fungi have only ASEXUAL reproduction. The most important methods of this kind of reproduction are the _sporangio-fructification_ and the _conidio-fructification_. In the SPORANGIO-FRUCTIFICATION the _spores_ (endospores) _arise inside_ a mother-cell, the sporangium (Fig. 80). Spores without a cell-wall, which move in water by means of cilia and hence are known as _swarmspores_ or _zoospores_, are found among the Oomycetes, the sporangia in which these are produced being called swarm-sporangia or zoosporangia (Figs. 86, 87, 91, 94). In the CONIDIO-FRUCTIFICATION the _conidia_ (exospores) arise on special hyphæ (conidiophores), or directly from the mycelium. When conidiophores are present, the conidia are developed upon them terminally or laterally, either in a basipetal succession (in many Fungi, for example in _Penicillium_, Fig. 111, _Erysiphe_, _Cystopus_), or acropetally (in which method the chains of conidia are often branched; examples, _Pleospora vulgaris_, _Hormodendron cladosporioides_). All conidia are at first unicellular, sometimes at a later stage they become two-celled or multicellular through the formation of partition-walls (_Piptocephalis_). The conidia with thick, brown cell-walls, and contents rich in fats (_resting conidia_), can withstand unfavourable external conditions for a much longer period than conidia with thin walls and poor in contents.