TAXONOMY 251 



SUB-CLASS B. OOMYCETES 

 (Sexual apparatus heterogamous) 



Order i. Chytridiales. Example: Synchytrium, a form para- 

 sitic on seed plants and forming blister-like swellings. 



Order 2. Saprolegniales. Water molds which attack fishes, 

 frogs, water insects, and decaying plants and animals. Example: 

 Saprolegnia. 



Order 3. Peronosporales. Mildews, destructive parasites, liv- 

 ing in the tissues of their hosts and effecting pathologic changes. 

 Example: Albugo, the blister blight, a white rust attacking members 

 of the Cruciferce and Phytophthora, producing potato rot. 



CLASS II. ASCOMYCETES, THE SAC FUNGI 



Mycelium composed of septate filaments and life history charac- 

 terized by the appearance of a sac called an ascus in which ascospores 

 are formed. The largest class of fungi. 



Order i. Protoascales. Plants with asci borne free or at the 

 ends of hyphae, definite fruiting bodies being absent. Each ascus 

 usually develops four ascospores. To this order belong Exoascus, 

 which is responsible for the abnormal development of tufted masses 

 of branches on a number of trees and shrubs, and the yeasts (Sac- 

 charomycetaceae) many of which produce fermentation. 



Yeasts are unicellular plants of spheroidal, oval, elliptical, pyri- 

 form or sausage shape which reproduce by budding. They occur 

 either in the wild or cultivated condition and are generally found 

 capable of breaking down some form of sugar into alcohol and carbon 

 dioxide. 



According to the kind or kinds of sugar fermented Hansen in 

 1888 classified the yeasts as follows: 



1. Species which ferment dextrose, maltose and saccharose: 

 Saccharomyces cerevisice I, S. ellipsoideus I, S. ellipsoideus IT, 

 S. pastorianus I, S. pastorianus II, S. pastorianus III. 



2. Species which ferment dextrose and saccharose, but not maj- 

 tose: Saccharomyces marxianus, S. exiguus, S. saturanus, S. Ludwigii. 



3. Species which ferment dextrose, but neither saccharose nor 

 maltose: Saccharomyces mail Duclauxii. 



