Minnesota Plant Diseases. 175 



paratively short — one-half inch or less in some forms — or they 

 may attain a length of three inches in others. They are chiefly 

 wood-inhabiting saprophytes and comprise some serious timber 

 rots and diseases; some are found on the ground. The coral 

 fungus and the very similar bear's-head fungus are exceedingly 

 common tooth-fungi, found on logs in autumn or throughout 

 the summer. The fruiting bodies of most of these fungi are 

 edible. (Figs. 81, 84, 119.) 



Pore fungi {Polyporacecs). This is one of the largest of the 

 groups of the palisade fungi and contains many of our most 

 conspicuous forms. They are palisade fungi which have in com- 

 mon the formation of pockets or pores in the fruiting body and 

 on the surfaces lining these pockets or pores are found the pal- 

 isades. A safe position and a great increase of spore area is 

 thus effected. There is considerable variety in these fungi in 

 respect of the consistency and form of the fruiting body. One 

 alliance of forms has more or less gelatinous fruiting bodies in 

 which ridges which cross and recross each other form shallow 

 pores. Many of these gelatinous pore fungi have single, pros- 

 trate fruiting bodies, though some form true shelves. Such 

 gelatinous pores resemble many of the trembling fungi and 

 their allies. To this group belongs the well known dry rot fun- 

 gus which is probably the most dangerous timber-saprophyte 

 known. They are common on rotting logs and stumps. The 

 majority of pore fungi have tough, leathery or more or less 

 woody fruiting bodies of a true shelf-habit. Most of our com- 

 mon shelf fungi belong to this group and they comprise a 

 great many of our most common timber diseases. A variation 

 is noticeable in the form of the pores and upon this variation is 

 based in a large measure the classification of the numerous 

 forms. Some pores are cylindrical, pockets, others are elon- 

 gated, and often fuse with neighboring pores and thus form 

 complex labyrinths; others, again, are hexagonal in outline. 

 The pores, moreover, vary in depth, in their relationships to sur- 

 rounding parts, in methods of formation, etc. Again, some 

 shelves last but one year while others live from year to year, 

 adding new substance to the fruiting body every year. In one 

 alliance of forms the shelves may be branched, forming large 

 compound shelves. The birch shelf-fungus, the sulphur fungus. 



