PUFFBALLS AND RELATED FORMS (GASTEROMYCETES) 389 
In Figure 344 is a Bracket Fungus which causes a disease 
known as White Heart Rot. This disease occurs on fruit trees 
and many forest trees. The spore enters through a wound and 
starts the mycelium which penetrates and transforms the heart 
wood into a white pulpy mass. In Figure 345 is shown another 
Bracket Fungus which attacks trees in a similar way and causes 
the wood to rot and become reddish brown or black. It produces 
the Red Heart Rot. There are many other destructive forms 
which concern the forester and horticulturist. They start in 
Fic. 344. — One of the Bracket Fungi, Fomes igniarius, living on the trunk 
of a living Aspen. It attacks various trees, destroying the wood and causing 
much damage. From Bulletin 189, Bureau of Plant Industry, U. 5. Dept. 
of Agriculture. 
wounds where there is some decaying matter, and in pruning it 
is necessary to guard against the entrance of these Fungi. 
Puffballs and Related Forms (Gasteromycetes). — On account 
of the complexity of their sporophores, the Gasteromycetes are 
considered the highest of all Fungi. They are saprophytes, 
growing on decaying wood, leaf mold, rich humus, and manure. 
They require about the same conditions for growth as do the Toad- 
stools and Mushrooms and are often found growing with them. 
There are about 700 species, many of which are edible. The 
sporophore of these Fungi is usually more or less globular in form 
and the hymenium is enclosed. 
