FUNGI 



remain near where they are produced and then develop typical repro- 

 ductive organs for the fungus when favorable conditions arrive. This is 

 the case with sclerotia of Claviceps, Sclerotinia, and some species of 

 Polyporus. From the sclerotia themselves under certain conditions new 

 mycehum may grow out instead of reproductive organs. This is the case 

 with the overwintering stage of a species of Pelliculana, the common black 

 scurf {" Rhizoctonia") of potatoes and other plants. 



Reproduction. Asexual reproduction in the true fungi may occur by 

 the formation within a zoosporangium of naked cells, zoospores, which 

 upon their release swim away by means of anteriorly, laterally, or pos- 

 teriorly attached flagella, either one or two in number depending upon 

 the order of fungi concerned. This production of zoospores is confined to 

 some orders of the Phycomyceteae. The zoospores eventually settle down 

 and encyst, and the encysted cell becomes the start of the new plant. In 

 the majority of fungi, including many of the Phycomyceteae and all of 

 the Higher Fungi in which asexual reproduction occurs, no motile spores 

 are produced but the spores are provided with a wall and are distributed 

 by air currents, by water, by insects, etc. These spores are of several 

 types of origin. In the Mucoraceae they are produced internally in a 

 sporangium; upon the rupture or dissolution of its walls, they are set free 

 and distributed by air or water currents. Such spores are sometimes called 

 aplanospores in contradistinction to the motile naked zoospores which 

 may be called planospores. Conidia arise as single separable cells of the 

 mycelium. They may arise by the fragmentation of the whole mycelium 

 or of special hyphae into cylindrical, ovoid, or spherical cells (oidial mode 

 of conidium formation) or by the cutting off of terminal or lateral cells 

 from special hyphae or conidiophores. In a number of genera the conidia 

 are pushed out one by one from the neck of a flask-like cell (or phialid). 

 The conidia, by whatever means they arise, may be hyaline or colored, 

 and may remain one-celled or by formation of transverse or longitudinal 

 septa may become two-celled to many-celled. They may be released 

 singly or remain attached in a chain. In some cases, instead of producing 

 conidia, a tangled mass of hyphae may form a rounded ball as in the 

 genus Papulospora. For the purpose of enabling the fungus to survive 

 unfavorable conditions such as cold, lack of water, etc., chlamydospores 

 are produced by many fungi. These are terminal or intercalary cells of a 

 hypha (or even single cells in a conidium made up of a row of cells) which 

 enlarge and round up, store supplies of food, and form a thick wall. Such 

 cells may live for years until favorable conditions arrive. They have 

 nothing to do with the sexual stage of the fungus so that the use of the 

 term chlamydospore for the reproductive cells (teliospores) of the 

 Ustilaginales is unwarranted. 



Sexual reproduction, or substitutes for it, may be found in most of 



