306 Ebport of the Horticulturist. 



Growth of Smutted Oat-plants. 



Since the smut parasite robs its host, the growing oat-plant, 

 of much nourishment, the latter is naturally much weakened, 

 and only a part of the smutted plants attain the average height 

 of healthy ones. The others are dwarfed more or less and often 

 to such an extent that they grow only a few inches high, A 

 large number of diseased plants, especially those much dwarfed, 

 are so weakened that they cannot push their panicles, or heads, 

 out of the sheath of the upper leaf. Upon opening these closed 

 heads they are found to be full of smut masses. Thus it is that 

 the casual observer sees only the high smut and concludes that 

 the crop is only slightly smutted. 



Infection of Seed Oats by Smut Spores. 



The seed is infected in several ways. Many of the spores ripen 

 before the oats do, are blown about by the wind and become 

 lodged on the ripening grain. In case the smut ripens early 

 while some of the oats are still in bloom the spores are liable to 

 become attached to the growing ovaries of the grain in such a 

 position that the glume or husk of the individual oat kernels 

 envelopes the spores, thus making it difficult to destroy them. 

 The wholesale agent of infection is the threshing machine, and 

 the crop from a field practically free from smut is liable to be- 

 come infected by spores carried in the machine from an infected 

 neighboring field. Then the use of sacks, grain bins, etc., that 

 have held smutted grain helps to distribute the smut spores. 



