ORDER USTILAGINALES (tHE SMUTs) 411 



each internode), on young, not yet unrolled leaves, on the male inflores- 

 cence (tassel) before it emerges, on the young ear or certain grains of the 

 ear and even on the elongated styles ("silks") on which N. F. Petersen 

 has shown that it may cause small galls. ^ Treatment of the grain with 

 disinfectants is of little value in controlling this type of infection. Planting 

 must be done in soil free from the fungus. 



3. Infection of the flower takes place at times of blooming. This was 

 worked out by Brefeld and Falck (1905). It occurs in the loose smuts of 

 wheat and barley, Ustilago tritici (Pers.) Rostr. and U. nuda (Jens.) 

 Kellerm. & Swingle, respectively. When the host plant has headed out the 

 flowers are normally self-pollinated before opening. When they open the 

 teliospores from nearby diseased plants germinate and produce their 

 sporidia or germ tubes on the stigmas and infect them, the germ tubes 

 growing down into the ovary and entering the developing embryo, in the 

 growing point of whose stem the mycelium becomes dormant until the 

 grain is planted. Then it grows rapidly in the apical meristem, apparently 

 causing Httle injury to the host plant until the head is being produced. 

 Within this developing head the mycelium grows very vigorously and 

 reduces it to a skeleton surrounded by the powdery masses of spores which 

 are set free at just the time the healthy plants are coming into flower. 

 Control is possible by soaking the infected grain and then dipping it into 

 hot water at a temperature and for a length of time that will kill the con- 

 tained mycelium without killing the grain. 



4. Another type of infection has been shown by Mundkur (1943) to 

 occur in the case of Neovossia indica (Mitra) Mundkur. In this smut the 

 spores or the smutted grains fall to the ground and under favorable condi- 

 tions the long promycelia produce up to 150 sporidia which are wind 

 borne and infect the kernels in the dough stage or a little earlier. These 

 kernels then become smutted that season. 



Smuts may cause large gafls consisting in part of host tissues and in 

 part of fungus tissues. The galls of maize smut ( Ustilago zeae) may attain 

 a large size and are edible when young. Various leaf smuts cause the pro- 

 duction of galls, e.g., Doassansia on the leaves of Sagittaria. Many smuts 

 on the other hand do not show their presence until their teliospores are 

 formed. Ustilago violacea (Pers.) Fuckel, attacks several species of Dian- 

 thaceae and Alsinaceae. Its teliospores are formed only in the anthers. 

 When the female plant of a dioecious species of Lychnis is infected the 

 presence of the fungus causes the flower to produce stamens, within which 

 the fungus produces its spores although the normal female flower lacks 

 stamens. 



The order is divided into two famihes which are almost certainly 

 closely related and to which a third family, Graphiolaceae, is probably 

 related. 



^ In a letter to the author. 



