410 CLASS BASIDIOMYCETEAE 



connections, especially since Stempell (1934-1935) grew various species 

 of Entyloma in culture and obtained typical clamp connections there. The 

 teliospores are produced largely in the flowers, fruits, and inflorescences, 

 but in many cases are produced in the leaves or stems. More often the 

 masses of teliospores are dusty at maturity, and with the rupture of the 

 host tissues are set free for distribution by the wind or other means. 

 The sporidia are shot from the promycelium with considerable force in the 

 Family Tifletiaceae accompanied by the formation of a droplet of water 

 at the apex of the sterigma a moment before the discharge of the spore. 

 Conidia are mostly produced on the saprophytic mycelium but in Tubur- 

 cinia and Entyloma they are produced abundantly on the surface of the 

 Hving leaves of the host plant on long conidiophores which emerge from 

 the epidermis and give a whitish appearance to the affected leaf. When a 

 conidium arises from a cell of monocaryon mycelium the nucleus of the 

 cell divides and one of the daughter nuclei passes out into the conidium 

 which grows out from one side of the hyphal cell. If the cells are binucleate 

 both nuclei divide simultaneously and one daughter nucleus of each pair 

 passes out into the developing conidium, or but one nucleus enters the 

 conidium (Paravicini, 1917). Thus it is possible for a conidium from a 

 monocaryon mycelium to produce a new mycelium only of the same sexual 

 phase, but that from a dicaryon mycelium may produce a dicaryon 

 mycelium or monocaryon mycelia of one or the other sexual phase depend- 

 ing upon which nucleus entered the conidium. (Fig. 137.) 



Liro (1935-1938) described conidia in the anthers of plants of Carda- 

 mine hellidifolia L., in whose pods the seeds were destroyed by Ustilago 

 cardamines Liro. The conidia cover and fill the discolored anthers. He 

 proposed for this conidial stage the name Rhombiella cardamines Liro. He 

 also described, under the name Crotalia cifitractiae-fischeri, the conidial 

 stage of Cintradia fischeri (Karst.) Liro, parasitic on Car ex canescens L. 



Infection of the host plant takes place only in meristematic tissues, by 

 means of sporidia or conidia or by a germ tube produced in place of a 

 sporidium. The Smuts fall roughly into four groups Avith reference to the 

 manner of infection: 



1. Infection takes place as the seed germinates, either from sporidia or 

 germ tubes produced on promycelia from teliospores adhering to the seed 

 or from sporidia or conidia present in the soil. This type of infection can 

 be controlled by treating the seed with suitable disinfectants before 

 planting them in soil free from smut. Examples are Ustilago avenae (Pers.) 

 Jens., oat smut; Tilletia foetida (Wall.) Liro {T. levis Kuhn) and T. caries 

 (DC.) Tul. {T. tritici (Bjerk.) Wint.), both of which cause stinking smut 

 or bunt of wheat; Urocystis occulta (Wall.) Ilab., causing stem smut of rye. 



2. Any actively growing meristem may be infected by sporidia or by 

 conidia. In the case of maize smut, Ustilago zeae, the infection may occur 

 on young roots, at any joint of the stem (i.e., the meristem at the base of 



