DISEASES OF ROSES 99 



smaller and bearing less foliage and less vigorous flowers. It 

 seems obvious that the energy used up in the production of galls, 

 which are often large, must be at the expense of the general needs 

 of the plant, resulting in an inferior product. 



Symptoms. Crown-gall exhibits itself in the production of galls 

 or tubercles, usually on the roots or the crowns of the plants, but 

 not infrequently on parts of the plant above ground. Smaller and 

 younger galls range in color from green to white and are soft and 

 spongy. As the galls become older they increase in size, frequently 

 reaching a diameter of several inches and darken in color externally. 

 The surface is rough, sometimes convoluted, and usually the galls 

 become firm and hard with age. 



Etiology. 



Crown-gall is a bacterial disease caused by Bacterium tume- 

 Jaciens Sm. and Town. 



The greater number of European observers assigned the cause of 

 the disease to physical agents, such as late frosts and winter killing. 

 Others thought the disease might be brought about by injuries 

 received from insects, while still others believed that the disease 

 was caused by bacteria, fungi, or slime-moulds, although the 

 pathogenicity of none of the suspected organisms was established. 



In April, 1907, Smith and Townsend (15) described a plant 

 tumor of bacterial origin, giving conclusive proof of the patho- 

 genicity of the organism Bacterium tumefaciens which was isolated 

 from the galls of the Paris daisy. Galls were produced on tobacco, 

 tomato, potato, sugar-beet, hop, and peach by artificial inocula- 

 tion. 



In December, 1908, at a meeting of the Botanical Society of 

 America, Townsend (16) reported the results of further experi- 

 ments with the organism from the Paris daisy. A bacterium was 

 isolated from a gall on roses and other plants which appeared to be 

 identical with that isolated from the daisy. The organisms from 

 the different hosts were cross-inoculable. Smith, Townsend and 

 Brown (14) report successful infections on the rose with the patho- 

 gene isolated from galls on this and other plants, and records 



