TAXONOMY 
^SI 
Sub-class B. —Oomycetes 
(Sexual apparatus heterogamous) 
Order 1.—Chy tridiales. —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 Crucifer ce and Phytophthora,'\)xo<\uomg 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 1.— 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 II, 
S. pastorianus I, S. pastorianus II, S. pastorianus III. 
2. Species which ferment dextrose and saccharose, but not mal¬ 
tose: Saccharomyces marxianus, S. exiguus, S. saturanus, S. Ludwigii. 
3. Species which ferment dextrose, but neither saccharose nor 
maltose: Saccharomyces mali Duclauxii . 
