1890.] PUBLIC DOCUMENT — No. 33. 209 



blueberry, cranberry, and related plants, to become swollen 

 and covered by a white " bloom," composed of the spores 

 of the fungus, and often does considerable damage. The 

 mycelia of several toadstools grow in the wood or between 

 the wood and bark of trees, and may do much harm to tim- 

 ber. In the case of some species, the mycelia may form 

 long, brown, branching sclerotia, somewhat resembling roots, 

 which are not uncommon beneath the bark of decaying logs. 

 This group includes the mushrooms, the chantarelle, and 

 many other valuable food fungi. 



10. Puff-balls {G aster omycetes) are nearly related to the 

 last group, and, like most of its members, aie saprophytes. 

 A few of the species are edible, but otherwise the group has 

 no economic importance, although including many familiarly 

 known forms. 



11. Yeasts (^Saccharomycetes) are very simple fungi, in 

 which the plant is reduced to a single elliptical cell, and 

 reproduces itself chiefly by a process of budding. A slight 

 projection grows out from the cell, and gradually increases 

 in size until it reaches dimensions not much less than those 

 of its parent cell, from which it then becomes detached, and 

 begins to lead an independent life, budding in its turn. 

 Although saprophytes, these fungi are of great interest 

 economically, from their producing the alcoholic fermenta- 

 tion, and their consequent practical application in baking 

 and brewing. The change known as alcoholic fermentation 

 consists in the separation of the chemical elements compos- 

 ing sugar, and their recombination into other compounds, 

 chiefly alcohol and carbon-dioxide ; and the power to pro- 

 duce this change is possessed in a remarkable degree by 

 some of the yeasts. 



12. Leaf -curls [Exoascem) are parasitic fungi of very 

 simple structure. They cause a swelling and curling of the 

 parts attacked, which are commonly the leaves, though 

 sometimes the fruits. The distortions are covered by a 

 "bloom" composed of tiny club-shaped sacs, projecting 

 from between the surface cells of the host, and containing 

 minute spores. The " curl " of peach leaves and the swell- 

 ing of unripe plums into "plum pockets" are caused by 

 these fungi. 



