Minnesota Plant Diseases. 



185 



the case may be. The distribution of the spores may thus con- 

 tinue for an unlimited period. Of course wind is the chief 

 agent of distribution. The earth-stars are puff-balls with usu- 

 ally three coats in the wall of their fruiting bodies. The outer 

 falls off and the median coat splits from the tip nearly to the 

 base in a number of places and each lobe, so formed, bends back 

 when it absorbs water, giving to the fruiting body the form of 

 a star. By this bending back of the lobes the puff-ball is broken 

 loose from its mycelium and raised up in the air. Thus the 



FIG. 93. Earth-stars. (Geaster triplex.) The uncovered strand mycelium of this fungus 

 is seen to the right, below; in the center and to the right above are unopened fruiting 

 bodies; above in the center is a star, just opening, and below to the left is a fully 

 opened or vaulted star with opened puff-ball in the center. Original. 



spores obtain a more advantageous position for distribution. 

 In most earth-stars this vaulted condition is permanent but in 

 one form (really, however, a wefted puff-ball) the coat opens and 

 closes depending on the presence or absence of water. The 

 bending back of the lobes is affected by the greater swelling 

 which takes place in the inner threads of this coat while the 

 outer threads are tough, remain somewhat rigid and are not 

 greatly extensible. One Minnesota earth-star which in the 

 younger stages is found just below the surface of the leaf mold 

 is able to lift itself out of the mold and becomes vaulted directly 



