CORN SMUTS AND THEIR PROPAGATION 143 



plant, they come into contact with an exposed surface of 

 young tissue, there they are capable of setting up a local 

 smut attack. Strange to say, they do not attack the seedling. 

 They do, however, attack the flower and can cause a purely 

 local stigmatic tubercle. The generalisation that young exposed 

 host tissue was liable to attack from wind-borne conidia, and 

 that in Zea the flowers presented such vulnerable tissue, led 

 Brefeld to suspect that probably other cereals are also liable 

 to infection in their flowers. Experiments in this direction 

 were started, but owing to difficulties of various kinds came 

 to nothing until Brefeld was appointed to Breslau, where, with 

 the help of Dr. Falck, an experimental plot, and a botanical 

 laboratory, the two observers during the past five years have 

 carried out their experiments successfully. The oat, wheat, 

 and barley were the three chief subjects of investigation. 

 Two methods of inoculation were tried. In the first the 

 inflorescence, when the flowers were judged to be open and 

 the stigmas ready for pollination, were placed in a glass 

 cylinder closed below by cotton wool. A number of smutty 

 flowers was, in the meantime, placed inside a rubber bag 

 with suitable tube and opening. By means of this sprayer 

 the smut spores were puffed into the cylinder and allowed 

 time to settle. The operation was not repeated for the same 

 spike or panicle, and as the flowers were not all in an open 

 receptive state the action could not be compared for effective- 

 ness with the possibilities in nature. Here the smutty heads 

 and the blooming healthy ones are simultaneously ripe, and the 

 smut spore can, one would expect, bombard the healthy flowers 

 from time to time as they become receptive, if flower inocu- 

 lation, as in Zea, occurs. The other artificial method tried 

 is more delicate. With the help of a lady's hand (says 

 Brefeld) and a fine camel's hair brush smut spores are placed 

 on the stigma and ovary wall of an oat or other cereal, as 

 little force as necessary being used to open wide enough 

 for the operation, the bracts of the flowers. In this way 

 many individual flowers can be, with certainty, inoculated. 

 Those not treated can be cut off. The method is more reliable 

 but slower than the cylinder one. 



Examination by microscope of some of the wheat flowers 

 a few days after inoculation showed that the smut spores had 

 sprouted in the stigmatic secretion and had sent hyphae into 



