FUNGI. 87 



String-like mycelia may be found, for example, in Phallus, 

 Coprinus, and are formed of hyp Jh.se, which run more or less 

 parallel to each other. Membrane-like mycelia are chiefly to be 

 found in Fungi growing on tree-stems (Polyporacese and Agari- 

 caceaa) ; 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 chiefly among 

 the lower Fungi w r hich stand near to the Algse, the Algal-Fungi, 

 and takes place by the same two methods as in the Algae, namely 

 by conjugation and by the fertilisation of the egg-cell in the 

 oogonium. It is also known in some of the Higher Fungi. 



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 hyphse (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. Ill, Erysiphe, 

 Cystopus), or acropetally (in which method the chains of conidia 

 are often branched ; examples, Pleospora vulgaris, Hormodendron 

 dadosporioides). 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 



