YEASTS (SACCHAROMYCES) 3v7 
Certain species! give desirable flavors to some kinds of cheese 
and are quite usetul in this connection. 
Naked-ascus Fungi (Protodiscales). — This is a small group of 
parasites which attack seed plants. They produce no ascocarp 
and the asci are therefore borne exposed (Fig. 328). So far as 
known they have no sexual reproduction. They are regarded 
as simple Ascomycetes. One common species is the Hxoascus 
deformans, which causes the disease known as Peach Curl. The 
mycelium develops in the tissues of the host and forms on the 
surface asci which appear as gray pow- 
dery films. One species attacks the 
young ovaries of Plums, causing the 
malformation known as ‘“‘ Bladder 
Plums,” and one species causes Witches’ 
Brooms on some of our deciduous trees. 
Yeasts (Saccharomyces).—The 
Yeasts are very simple Ascomycetes. 
In most Yeasts the hyphae are so short 
and simple that they appear as single Fic. 329.— Bread Yeast. 
globular cells The only reason for pacehinomuyses eorenisine.. .G, 
i i single plant (Xx 600); b, a 
calling them Ascomycetes is that under plane an theeproceaser wank: 
certain conditions the cells form spores ding; c, plant which has 
and then resemble asci (Fig. 329). formed spores; d, plants re- 
On account of their ability to fer- git ee span and 
ment sugars and produce carbon dioxide ‘Mg chains as they are 
and ea hee are useful in making maple by Pussies, 
bread and in making alcohol, wine, 
beer, and other liquors which contain alcohol. When placed in 
dough they grow and work rapidly, and the carbon dioxide pro- 
duced causes the bread to rise. There are many kinds of Yeasts, 
and each kind gives a different flavor to the fermented product. 
For this reason brewers keep pure cultures of certain kinds of 
Yeasts, which give the liquor the desired characteristics. 
Their main method of reproduction is by the rapid division of 
cells, often called budding, in which small cells are apparently 
pinched off from the parent ccll. The cells often remain in 
contact for some time after being budded off, forming chains of 
cells. 
1 Cultural Studies of Species of Penicillium. Bulletin 148, Bureau of 
Animal Industry, U. 8. Dept. Agriculture, 1911. 
