184 MYCOLOGY 



tion of these parts. In germination, a promycelium is formed, which 

 usually gives rise to a terminal cluster of elongated basidiospores, or 

 sporidia, which sometimes bear whorls of secondary basidiospores. 

 Sometimes the primary sporidia fuse in pairs, and these with or without 

 fusing may give rise to infection hypha?; or in nutrient media to a 

 mycehum bearing dissimilar secondary sporidia (aerial conidia). As 

 in the preceding family the hyphae break up into chlamydospores which 

 break through the host tissue, as a sooty mass of dust. When these 

 chlamydospores germinate, they give^ rise to an undivided basidium 

 with basidiospores borne at the apex not on the side, as in the preced- 

 ing family. This is the principal morphologic difference, as the two 

 groups of smut fungi approach each other so closely t^iat in external 

 appearance they resemble each other. Brefeld described the structure 

 and life history of Tilletia tritici {T. caries), the bunt of wheat very 

 carefully. In England, this disease of the wheat plant is called in 

 various districts pepper brand, smut balls, bladder brand, stinking 

 smut, stinking rust (Fig. 63) In the fields, it is difficult to distinguish 

 diseased from sound wheat, as there is little to indicate the presence of 

 the hidden parasite, but it excites an abnormal development of chloro- 

 phyll, so that the spikes of the affected plants are usually greener than 

 the healthy ones. The brand spores are found in all the grains of a single 

 ear. The burst grains are shorter and wider than healthy ones and 

 pointed toward the base. When cracked, a black dust is discharged, 

 which under the microscope is seen to consist of reticulate-walled spores 

 of an olive-brown. They germinate readily and even after eight and a 

 half years, they have been known to grow. On rubbing the black 

 powdery mass between the fingers, the smell of herring brine is given 

 off, and this decayed fish odor has originated one of the common 

 names, that of stinking smut. A curved unicellular basidium arises 

 from the chlamydospore on its germination. This produces a bundle 

 of elongated condiospores, or basidiospores, according to one's bias. 

 Sickle-shaped secondary conidiospores arise from the primary kind. 

 The primary conidiospores may unite by bridge-like connections so 

 that two united spores look like the letter H. Wheat becomes infected 

 in the seedling state, the spores being sown with the grain, and the 

 infection hypha which enters the host forms a mycelium which grows 

 along with the host until the spores break out again. 



Tilletia is the most important genus. In it the sori may occur in 



