176 Plant Biology 



globose tips of these hyphae (Fig. 38). In many ways the Aspergillus 

 molds resemble the Penicillium molds, but the tips of the conidiophores 

 differ in their specific methods of producing the conidia (Figs. 38 and 

 73). 



Aspergillus is classified as an Ascomycete because certain hyphae may 

 produce ascos pores within saclike asci. Species of Aspergillus cause the 

 spoilage of bread and other foods, the deterioration of leathers and fab- 

 rics, the decay of tobacco, and the rotting of fruits. Certain species may 

 cause lung and ear infections in animals, including man. Certain species 

 of Aspergillus may be used commercially in the production of alcohols 

 and organic acids. 



3. Cup Fungus (Peziza) (pe-zi'za) (L, pezica, sessile fungus) (Fig. 

 40). — The so-called cup fungi possess a fleshy, cuplike body {ascocarp) 

 specifically called an apothecium (ap o -the' si um) (Gr. apo, away; 

 thece, cup) which is composed of tightly compacted hyphae and which is 

 often borne on a stalk. Inside the cup is a layer of cylindroid or sac- 

 shaped asci and sterile hyphae called paraphyses (pa -raf i sez) (Gr. 

 para, beside; physis, growth). The asci and paraphyses constitute a 

 layer called the hymenium (hi -me' ni um) (Gr. hymen, skin). The 

 asci usually contain eight ascospores. 



There are over 5,000 species of cup fungi, many of which are sapro- 

 phytes on decaying vegetable matter, on dead wood, or on the ground. 

 Some species may be brilliantly colored, and in some the saucer-shaped 

 fruiting body may be four inches in diameter. 



4. Yeasts (ye' st) (A.S. gist, ferment) . — Yeasts are typically unicellular, 

 saprophytic fungi usually without hyphae, although a few species may 

 develop a short hypha (Fig. 37) . Each cell is usually ovoid in shape and 

 contains an organized nucleus. Asexual reproduction is commonly accom- 

 plished by budding in which a small protuberance {hud) is projected 

 from the cell. The bud may free itself from the mother cell or remain 

 attached and produce more buds, eventually forming a many-celled 

 chain of cells. 



Under certain conditions a yeast cell may become a simple, single 

 ascus in which are formed ascospores (usually four). In other instances 

 two yeast cells may fuse before the ascospores are produced. 



Yeasts are of economic importance in the production of alcohol from 

 sugars, in the rising of bread by the production of carbon dioxide, in 

 manufacturing certain vitamins, and by being parasites on higher plants, 

 animals, and man. A yeastlike organism causes "leaf curl" on peach 



