TILLETIA. 309 



ceased, begin to thicken, at first equally, then more at some 

 places than others, so that they become nodose or rosary-like, 

 with swellings at irregular intervals. The spores originate in 

 the swellings, and between them are formed cross-septa which 

 split and bring about isolation of the spores. 



Kiihn's experiments on infection are of considerable interest. 

 He investigated the germination of this and other smut-fungi, 

 cultivating many of them in his garden at Halle, and published 

 his results as early as 1858.^ In his artificial infections he 

 dusted seedlings with spores of Tilletia, and investigated the 

 different parts of them microscopically. Sections showed him 

 that the germ-tubes penetrate direct through the walls into 

 the epidermal cells, and always in the neighbourhood of the 

 lowest nodes. Thence the mycelium grows upwards with the 

 lengthening plant, especially through the pith, and the plasma 

 of the older mycelium passes onwards into younger parts. In 

 this way the hyphae, without greatly disturbing the growth of 

 the wheat-seedlings, reach the ovaries, and with the formation 

 of spores begin the work of destruction. 



Klihn was also able to demonstrate that both germinating 

 sporidia and conidia are capable of infection, and that, where 

 many had infected the same plant, so much mycelium could be 

 produced that death of the host ensued. According to the 

 same authority, the fungus attacks spring wheat more than 

 winter wheat, and the common forms {Triticum sativum and 

 T. timjidum) with nearly allied varieties, more than " spelt " 

 ( Triticum spelta). 



As a preventive measure against Tilletia, the experiments of 

 Kellermann, Swingle, Kirchner, and others, lead them to recom- 

 mend Jensen's method of placing the seed in hot water immedi- 

 ately liefore sowing. (See Chap. VI.) 



Tilletia laevis Klihn. (U.S. America.) This is another stink- 

 ing smut of wheat similar to T. tritici, except that its spores 

 have perfectly smooth coats. 



T. controversa Klihn. Found in grains of Triticum repcns 

 (couch-grass) as well as Tr. vulgarc and Tr. fjlauciim. The 

 spores are distinguished from those of T. tritici by the higher 

 ridges and wider meshes on the episporium. The mycelium 



^ Previous to Kiihn, Prevost and Tulasne had in 1853 carried out experiments ; 

 also Gleichen in 1781. 



