39 



spores are very small and are easily carried by the wind, as they float 

 in large numbers in the air. Owing to this, the diseases caused by 

 fungi Sjjread very easily. 



One of the simplest fungi is the Yeast plant {Saccharomyces). It 

 possesses no mycelium, consisting simply of a single, oval cell. Spores 

 are seldom, if, ever, formed. It rep'oduces itself by bud ling, /. e. by 

 bulging out at some point till the protuberance resembles the parent 

 cell and is separated trom it by a wall. To study its growth a raicros- 

 coi)e magnifying 400 to 600 diameters and an artificially heated slide 

 are necessary. It lives on materials containing grape sugar and has the 

 power of splitting the latter into carbonic acid and alcohol. The man- 

 ufacturer of beer is largely dependent on this lower form of life, for it 

 transforms the sugar produced from the starch by the sprouting or mal- 

 ting of barley into the alcohol found in beer. But it does not 

 assist man only in the manufacture of beer, wine, cider and other alco- 

 holic beverages or the products, like vinegar, derived from the same; 

 but performs an almost equally important role in the productio;'i of ''the 

 staff of life." The yeast growing in the dough gives rise to successive 

 little bubbles of carbonic acid gas which retained by the latter till baked 

 causes the rising of tie dju^h aid the production of a light and 

 more easily digested bread. 



A more typical fungus, the various stages of which are shown in 

 some of the microscopes before you, is the one producing the disease 

 known as " Rust " on the various grains and grasses. This disease, 

 most prevalent in wet seasons on heavily manured soi!s, is generally 

 first noticed by the appearance of reddish-brown s[)ots on the leaves and 

 stems of cereals, which rapidly multiply till the grain ripens. These 

 spots consist of loosly attached, unicellular, oval, somewhat spiny, 

 reddish-brotvn spores, which carried by the wind, birds or insects to 

 other places, quickly germinate, producing a mass of mycelium and in 

 turn another crop of similar spores. These successive crops of «rf^(? 

 spores, as they are called, continue to be produced till the nutriment m 

 the straw lessened by the ripening of the grain and the growth of the 

 fungus is not sufficient to support a vigorous growth of the latter. The 

 parusite then terminates its growth for the season by the production of 

 a somewhat larger, dark brown, two-celled resting spore seen on the 



