232 THE BASIDIA-FORMING FUNGI 



siderable distances, owing to the accumulation of fluids in the 

 asci which finally rupture at their apices. In some forms, the 

 entire ascus is discharged with an audible explosion, owing to 

 the swelling and rupture of the supporting hyphae. The bright 

 scarlet cups of Sarcoscypha, common in the spring on decaying 

 sticks and the gray cups of Peziza growing upon the ground 

 and decaying wood, are familiar examples of the order. 



92. Order h. Helvellales. — These are fleshy forms in which 

 the hymenium is exposed over the surface of a variously shaped 

 ascocarp, as shown in the common genera illustrated in Fig. 

 158. The morel or M or chella, in which the hymenium is spread 

 over the pitted or honey-combed surface of the ascocarp, is one 

 of the most highly prized of the edible fungi. The members of 

 this order are largely saprophytic and often attain considerable 

 size, forms of Morchella occasionally reaching the height of a 

 foot and some species of Gyromitra weigh over a pound. 



Class C. Basidiomycetes or Basidia-forming Fungi 



93. General Features. — This class contains two important 

 groups of fungi; one of which includes very destructive para- 

 sites, and the other comprises those conspicuous and familiar sap- 

 rophytes known as mushrooms, bracket fungi, puff balls, etc. 

 The striking feature of the class is the formation of spores on 

 club-like hyphae called basidia (sing, basidium) (Fig. 168, D). 

 These organs are often developed in rather complex outgrowths 

 of the mycelium which may be fleshy or woody, as in the mush- 

 room and bracket fungi (Figs. 167; 170, B). There is no known 

 sexual reproduction, save possibly in the first order mentioned 

 below. The more important orders are the following: 



94. Order a. Uredinales or Rusts. — These parasites are well 

 known by the streaks and blotches of yellow or black rust which 

 they produce on the leaves and stems of a great variety of plants. 

 About 2,000 species are known in the United States. They are 

 among the most destructive parasites, causing great damage to 

 wheat, oats, apples, quinces, roses, carnations, etc. The yearly 

 loss from grain rust alone is estimated at considerably over 

 $18,000,000 in the United States. They exhibit a degree of 



