Minnesota Plant Diseases. 



137 



dense crops of very small, black, thickly-crowded, pear-shaped 

 bodies. These often bear crowns of dark tangled hairs surround- 

 ing an opening at the tip. They are sac-spore capsules and dense 

 masses of spores can be seen 

 collected near the opening 

 or scattered as a dense 

 brown or black dust around 

 the capsules. The latter 

 are formed singly and some- 

 times but not usually up- 

 on mycelial masses, as is 

 the case in black knot, cat- 

 erpillar fungus and ergot. 

 The spores occur usually 

 eight in a sac and often 

 have curiously-shaped tail- 

 like appendages. These 

 fungi (Sordariaceae) are 

 very abundant and at first 

 sight seem insignificant but 

 are of some importance 

 nevertheless. The dung of 

 horses is made up largely of 

 the indigestible woody 

 parts of plants, e. g., the 

 veins of the leaves of 

 grasses, and it is on these that the fungus feeds, disintegrating 

 them as wood-destroying fungi do timbers. 



Another group of forms (Chsetomiacese) closely allied to the 

 dung fungi is found chiefly on moldy paper. Here the sac cap- 

 sule is provided with great twisted and tangled masses of crown 

 hairs in which the spores are lodged after ejection from the 

 sacs and sac-capsules, and are later from this point shaken out 

 and distributed. Building paper is often rotted by these fungi. 

 (Fig. 60.) 



Sphere-fungi and their allies (Pyrenomycetinea (in part) in- 

 cluding Sphceriacecc and other families). This is one of the very 

 largest groups of fungi, rivalled in point of numbers only by 

 the mushroom allies and cup fungi. It is also of great impor- 



FIG. 60. Above is seen a sac-capsule of a dung 

 fungus (Sordariaceae) showing the escaped 

 sacs, which are cylindrical and contain 

 each eight spores. Broken sacs and free 

 sac-spores are also seen. Below are two 

 sac-capsules of another fungus of this 

 group (Chaetomiaceae). At the summit of 

 the fruiting body are seen great tangles of 

 twisted threads in which the spores are 

 caught. Magnified. Microphctograph by 

 F. K. Butters. 



