Infection. 35 



Dr. Hecke comes to the conclusion from these experiments '' that besides 

 the seecIHng and flower infection, there is still another kind of infection among 

 smuts, that is to say, shoot infection. It is probable that this kind of infection 

 occurs not only with Ustilago violacea and Urocystis occulta, but also with 

 other smuts as well. The smuts of perennial plants are especially considered 

 here, but it is possible that the same thing occurs in the case of infected shoots 

 of cereals. A series of experiments of this kind is being carried out with 

 different smuts, the results of which will be given later." 



This will account for the infection of the shoots of cereals by Urocystis 

 occulta or flag smut, by these 5'oung and tender shoots coming into contact 

 with the diseased straw and other spore-bearing material in the soil, in the 

 process known as " tillering." When the primary or terminal bud has about 

 reached the surface of the ground, then lateral buds mav be formed in the 

 axils of the leaves about the same position. These lateral buds or " tillers " 

 as they are sometimes called, usually develop into branches, and these 

 branches may in turn produce other branches, so that from a single grain of 

 wheat a plant may be developed consisting of numerous stalks each bearing 

 an ear. Such an individual plant with numerous stems arising from a 

 common root is usually called a " stool " and the process by which the plant 

 thus adapts itself to its environment is known as " stooling " or " tillering." 

 This branching takes place at the joints or nodes near the surface of the 

 ground and as many as 125 stalks of Steinwedel wheat with 12.5 perfect ears, 

 with an average of fifty grains in each ear have been recorded and photographed 

 by Thompson' in New South Wales. It is evident that the smut fungus may 

 enter these numerous stalks, either by directly infecting the young seedling, 

 or by gaining an entrance through the young shoots, or, as in the case of plants 

 living more than one year, by a perennial mycelium.. 



The case already given of a smutted barley plant being cut back and the 

 fresh shoots being again infected by the mycelium persisting in the lower 

 nodes, shows that we have to distinguish between infection of the shoots from 

 without and from within. 



Collection of Spore Material. 



For successful infection it is necessary to have the material as fresh and as 

 well preserved as possible and taken direct from the fields where it is produced. 

 To preserve it in the best possible condition for the following spring requires 

 care and attention, for if special precautions are not taken, it may be injured 

 by moulds or by grubs so as to be quite useless. To guard against 

 such injurious influences, Brefeld adopted the following method of 

 collecting and preserving plenty of pure spore material as the result 

 of a lengthened experience. It should be gathered in sufficient ([uantity 

 soon after the exposure of the spores, before grubs or moulds can gain access 

 to it and preserved for about a week in a dry place. Then the spores are passed 

 through a fine sieve on to white paper and the residue is thrown away. The 

 result is that the spores which have passed through the sieve are in a powdery 

 and dry condition, and keep well until the next spring. The spores are next 

 placed in small tubes, only filling them to about a quarter of their capacity, 

 and the neck is securely closed with sterilized paper before laying them aside 

 in a cool dry place during the winter. A number of these tubes are filled, so 

 that if some should happen to deteriorate, the others mav be perfectly pure. 



Just before using the spores in the spring for the infection of the young 

 seedlings, they were placed in pure water and thoroughly stirred up in the 

 centrifuge. This treatment of the spores and leaving thein to settle for one 

 day in the water, not only cleaned them thoroughly but rendered them most 



