70 Stiiiknig S/nui or Baut in VC Jicat. 



CHAPTER XII. 

 Stinking Smut or Bunt in Wheat. 



{TUletia tritici (Bjerk.) Wint. ; T. levis, Kuehn.) 



Perhaps there is no smut better known to the AustraUan farmer than 

 this one, since although it remains enclosed until harvested, it gives forth a 

 disagreeable odour like stinking fish, especially when crushed, and one cannot 

 fail to detect its presence. The spores do not escape as a powder, but are 

 enclosed in the ovaries and glumes, and although at first somewhat greasy, 

 they soon become dry and hard ; and the mass of spores in an ovary is known 

 as a bunt-ball, hence it is frequently spoken of as ball smut, and sometimes, 

 on account of its hardness, as stone smut. Since the spores do not burst 

 through, but are enveloped by the outer coats of the ovaries, it requires the 

 practised eye to detect the disease at first (Plate II.). The ears are rigid, 

 and of a somewhat darker green colour than the normal, the spikes are rather 

 smaller, and a little further apart, and stand out more from the axis of the 

 inflorescence, and the grains themselves in the early stages are of a deep 

 dark unhealthy green, and the upper straw is of a peculiar bluish-green 

 colour. The growth is arrested earher than in healthy plants, so that there 

 is premature ripening, and the leaves indicate the diseased condition by 

 their yellow colour. There is the disagreeable smell where the disease is 

 plentiful, which is due to trimethylamin, a decomposition product of the 

 nitrogenous constituents of the parasite. 



There are two species of smuts responsible for this disease, the one with 

 smooth and the other with netted spores, but as both sometimes occur in 

 the same ear of wheat and generally agree in their life history, they will be 

 treated here as practically the same. 



Germination. 



This was one of the first species in which the germination of the spores of 

 smuts was observed. Prevost^ in 1807, germinated them in water, and figured 

 not only the promycelium, but also the primary and secondary conidia. 

 These observations were confirmed by a number of later observers, and 

 Tulasne\ in 1854, investigated the subject more fully. In 1858, Kuehn^ 

 fully described the process, and then, in 1883, BrefekV added to our knowledge 

 by showing how the spores behaved in a nutritive solution. 



The spore germinates in water or after being kept damp for two or tliree 

 days. The spores germinate freely under the following conditions : — Place 

 them on damp blotting paper on a plate under a bell jar, keeping them moist 

 for a few days, and the fine white mould which soon appears constitutes the 

 promycelia and the numerous sickle-shaped conidia of the germinating 

 spores. Or take a plate of plaster of Paris sprinkled with spores and place 

 it in water under a bell jar. In about three days there is a copious production 

 of conidia. The outer membrane of the spore splits, and a stout promycelium 

 of varying length is produced, which elongates at the apex. When this 

 reaches the air a tuft of thread-like branches is formed at the apex, and these 

 constitute the conidia. After all the protoplasm has passed into them from 

 the promycelium, they are cut off by a cross partition or septum, and if the 

 promycelium happens to be very long, then numerous septa are formed from, 

 below upwards. The length of the promycelium will vary according to th 

 distance to be traversed before it reaches the air, since conidia are only forme 



