184 Minnesota Plant Diseases. 



into the air. The spores begin to germinate in the mass and 

 thus a new mycelium is started. These fungi are wood-inhabit- 

 ing saprophytes and are frequently found on pine wood, as on 

 decaying sidewalk planks. (Figs. 14, 81.) 



Underground puff -balls (Hymenogastracea). These fungi 

 form their fruiting bodies under the ground, sometimes an inch 

 or more below the surface. They are often thick-skinned and 

 never open except by the decay of the walls. The interior does 

 not develop a spore-powder mass but remains chambered to 

 maturity, and the chambers are lined with palisades of basidia. 

 These fungi are saprophytic. They are not abundant in Minne- 

 sota though several forms are known. They resemble very 

 much the true and false truffles, but, of course, differ from these 

 in the method of forming spores, for the puff-ball spores are 

 never found in sacs but always on a basidium. 



True puff-balls and earth-stars (Lycoperdinecc). This group 

 includes many exceedingly common fungi which can be found in 

 great abundance in early fall. The puff-balls are therefore very 

 familiar objects. The fruiting body is usually spherical and is 

 always at least at maturity found on and never below the surface 

 of the ground. It is usually provided with at least two coats, 

 the outer of which is shed in various ways and the inner coats 

 peel off, undergo splitting, or open by a definite pore-like aper- 

 ture. In one group of very common puff-balls, the outer coat 

 forms small bosses, or more or less elongated spines, which at 

 maturity fall off (Figs. 90 and 91) and leave characteristic scars 

 on the inner coat. 



One of the most familiar of this group is the gemmed puff- 

 ball in which the short spine-bosses are grouped together in 

 clusters. Some true puff-balls have paper-like and very thin 

 coats and our common form of this group is almost perfectly 

 spherical. The outer coat peels off in shreds and the inner 

 opens by a pore. In still other forms the puff-ball's outer coat 

 splits along the equator and the upper half then becomes in- 

 verted and looks like a saucer containing a puff-ball. The puff- 

 ball fruiting body always contains its spores in a powdery mass 

 which lies loosely in a cotton-like tangle of sterile threads. 

 When jarred in any way the puff-ball emits clouds of spores 

 which look like dust, olive-green, brown or black-purple, as 



