390 THALLOPHYTES 
The most common and familiar members of the order are the 
Puffballs, common in the woods and fields, and so named because 
when pressed upon the spores puff out in cloud-like masses 
(Fig. 346). Some of the Puffballs are a foot or more in diameter 
when mature and most of them are edible. The sporophore 
Fic. 345.— A Polyporus Fungus, Polyporus sulfureus, on the Red Oak. 
It causes the Red Heart Rot of trees. Photo by Dr. W. A. Murrill, N. Y. 
Botanical Garden. 
develops from a subterranean mycelium, and is differentiated 
into an outer region which constitutes a two-layered skin-like 
covering (pertdium) and an interior chambered region (gleba) in 
which the basidia intermingled with sterile hyphae occur. Spores 
are produced in immense numbers. A Puffball of ordinary size 
produces many millions of spores. The spores are dark in color 
due to their heavy walls. They escape from the sporophore 
through pore-like or slit-like openings in the peridium. 
