' BUNT ' OR STINKING-SMUT OF WHEAT 723 



with smut-spores obtained from wheat-ears. Sow these grains, and near them 

 sow 50 more grains from an ordinary sample of wheat. Allow them to grow, 

 and note which is most smutted. 



Ex. 293. — Sow small sample of grain dressed in the various ways mentioned 

 in ' Prevention and Remedies for Smut,' pp. 717 to 719, and observe the be- 

 haviour of each as regards germinating capacity and rapidity of germination. 



4. Many other species of the genus Ustilago are met with 

 on grasses, sedges, various Compositae, Polygonaceae, and other 

 plants. 



Maize smut, Ustilago Maydis D.C., gives rise to large deforma- 

 tions on the ears, leaves, and stems of the maize plant. The 

 malformations are at first white, and are subsequently filled with 

 millions of dark-coloured chlamydospores, which have a finely 

 spinous or warted epispore. 



(2) Tilletiacex. 



5. As an example of the Tilletiacese or second family of the 

 Hemibasidii, the ' bunt ' of wheat may be studied. 



'Bunt' or Stinking-smut of Wheat. — Wheat plants affected 

 with this disease are in their early stages of growth generally a 

 darker bluish-green colour and more robust and luxuriant in ap- 

 pearance than healthy plants. When the ear is ripe it remains 

 stiff and erect ; the bunted grains within it are found to be plumper 

 and shorter than normal grains, and filled with a black, some- 

 what oily powder, which possesses a disagreeable odour of stale 

 herrings. The glumes of the ears look white and bleached, and 

 on account of the thickness of the grains within them they are 

 pushed apart more than the glumes of healthy ears. 



' Bunted ' grains communicate their dark colour and very 

 objectionable odour to flour when they are ground in a sample 

 of wheat. 



The black powder within the grains are the chlamydospores 

 of the fungus Tilletia Tritici Bjerk. ( = Tilletia caries Tul.). Each 

 chalmydospore is spherical, and three or four times the diameter 

 of a spore of Ustilago Tritici. The exospore is brown, and covered 

 with irregular, net-like thickenings (a, Fig. 244). On germina- 



