Minnesota Plant Diseases. 



155 



the most destructive disease-causing alliances of the whole 

 group of the fungi. As food producing fungi, the stalked fun- 

 gus group is very important since all of the true mushrooms, 

 the edible pore fungi, club and tooth fungi, as well as the great 

 variety of puff balls are found in this group. 



The basidium-bearing fungi comprise the following twelve 

 groups. Of these the last eleven possess true basidia, i. e., 

 with a definite number of stalks and spores which are usually 

 definitely arranged as at the summit or on the sides. In the 

 smuts, however, the basidium, if so it may be called, bears a 

 great number of spores which are budded off in yeast fashion 

 from the side of the basidium cells. In other words the basid- 

 ium of the smuts has not attained to the definiteness of the 

 other basidium-bearing fungi and the smuts are often classed as 

 a group outside of these. (For figures, see following groups.) 



Smuts (Ustilagine&). Though not a very large group of 

 fungi the smuts are very important from the economic stand- 

 point because they contain many disease-producing forms. 

 The smuts possess the simplest form of 

 basidium found in the stalked fungi. They 

 are all parasitic and many of them are 

 half-parasitic in habit, since they are able 

 to live in certain stages for an indefinite 

 period in culture media. They can, how- e/ 

 ever, complete their life-story only as para- 

 sites on certain plants. The basidium 

 arises directly from a resting-spore which 

 is commonly known as the smut spore, , 

 producing the so-called smut of grain and ^ 

 of other plants. This smut or resting 

 spore is usually black, dark-brown or dark- 

 green in color and has a thick outer coat, 

 which, under favorable conditions of moist- 

 ure, breaks open and allows the inner wall 

 to be shoved out in the form of a thread. 

 This thread grows out to six or more times 

 the length of the spore. It then becomes 

 divided by cross-walls into three or four 

 cells, each of which buds off an indefinite 



-el 



FIG. 71. S m u t spores, 

 germinating; cl the 

 smut spore, t the thread 

 growing from it, and c 

 the spore produced by 

 the tube. 1. Wheat 

 smut the thread is di- 

 vided up by cross walls 

 into cells, each of 

 which buds off spores 

 from its side. 2. 

 Stinking smut of wheat 

 the thread from the 

 spore is undivided and 

 produces a crown of 

 thread-like spores at the 

 top. Highly magnified. 

 After Brefeld. 



