FUNGI: MUSHROOMS. 199 



linia. Sometimes they are united to form a crust which is partly formed 

 from sterile elements as in Hypoxylon, or they form black clavate or 

 branched bodies as in Xylaria. The black knot of the plum and cherry is 

 also an example. 



The lichens are mostly ascomycetes like the black fungi or cup fungi, 

 while a few are basidiomycetes. 



417. The morels (Morchella). There are several species of morels 

 which are common in early spring on damp ground. Either one of the 

 species is suitable for use if it is desired to include this in the study. Fig. 

 23 1 a illustrates the Morchella esculenta. The stem is cylindrical and 

 stout. The fruiting portion forms the "head," and it is deeply pitted. 

 The entire pitted surface is covered by the asci, which are cylindrical and 

 eight spored. A thin section may be made of a portion for study, or a 

 small piece may be crushed under the cover glass. 



418. The cup fungi. These fungi are common on damp ground or on 

 rotting logs in the summer. They may be preserved in 70 per cent alcohol 

 for study. Many of them are shaped like broad open cups or saucers. 

 The inner surface of the cup is the fruiting surface, and is covered with the 

 cylindrical asci, which stand side by side. A bit of the cup may be sec- 

 tioned or crushed under a cover glass for study. 



Mushrooms (Basidiomycetes). 



419. The large group of fungi to which the mushroom belongs is called 

 the basidiomycetes because in all of them a structure resembling a club, 

 or basidium, is present, and bears a limited number of spores, usually four, 

 though in some genera the number is variable. Some place the rusts 

 (Uredineae) in the same series (basidium series), because of the short pro- 

 mycelium and four sporidia developed from each cell of the teleutospore. 



420. The gill-bearing fungi (Agaricaceae). A good example 

 for this study is the common mushroom (Agaricus campestris). 



This occurs from July to November in lawns and grassy fields. 

 The plant is somewhat umbrella-shaped, as shown in fig. 232, 

 and possesses a cylindrical stem attached to the under side of the 

 convex cap or pileus. On the under side of the pileus are thin 

 radiating plates, shaped somewhat like a knife blade. These are 

 the gills, or lamellae, and toward the stem they are rounded on 

 the lower angle and are not attached to the stem. The longer 

 ones extend from near the stem to the margin of the pileus, and 

 the V-shaped spaces between them are occupied by successively 



