ORDER USTILAGINALES (tHE SMUTS) 



409 



Arth., on Phaseolus vulgaris L.; Melampsora lini (Pers.) Lev., on flax; 

 Cronartium ribicola Fischer, on white pine {Pinus strohus L.). Several 

 species of rusts are harmful to ornamental plants. 



Order Ustilaginales (The Smuts). The Smuts are parasitic, but ca- 

 pable of growth as saprophytes on substrata rich in organic material, e.g., 

 well-manured fields. Flerov (1923) and Sartoris (1924) grew several species 

 of Ustilago through to teliospore production on artificial culture media 

 apart from their hosts. Recently Leach and Ryan (1946) grew Ustilago 

 striiformis (West.) Niessl. from teliospore to teliospore. Kniep (1911) ac- 

 complished this with Urocystis anemones (Pers.) Schroet. and Wernham 

 (1938) with U. gladioli (Req.) Sm. In the host plant the mycelium is at 

 first intracellular (Kolk, 1930) and later intercellular, with or without 

 haustoria, and actually growing in and keeping pace in its growth with 

 that of the meristematic regions of the host, usually dying in the portions 

 that have passed that stage. A few species parasitic on perennial hosts 

 live over winter in the crown of the plant so that the new growth becomes 

 diseased. Seyfert (1927), investigating several smuts in Europe and Stak- 

 man and Christensen (1927) studymg Ustilago zeae (Beckm.) Unger, and 

 Hanna (1929b), investigating the same species seem to have demon- 

 strated clearly that clamp connections are often present in the dicaryon 

 stage of growth. Sleumer (1932) however, claims that these are not true 

 clamp connections but abortive branches. The nuclear behavior as re- 

 ported by Seyfert would support the idea that they are typical clamp 



Fig. 137. Subclass Teliosporeae, Order Ustilaginales. (Left and center) Family 

 Ustilaginaceae, Ustilago levis (Kellerm. & Swingle) Magn. (Left) Mycelium in meri- 

 stem of growing tip of seedling of Avena sativa L. (Center) Piece of intercellular 

 mycelium. {Right) Family Tilletiaceae, Urocystis anetnones (Pers.) Wint.; haustorium. 

 (Courtesy, Lutman: Trans. Wisconsin Acad. Sci., 16(2):1191-1244.) 



