200 CEOWN-GALL OF PLANTS. 



celled or spindle-celled hyperplasia; great reduction of amount of 

 conductive tissues; early necrosis, especiall}'- of the more fleshy 

 tumors, with renewed growth at the margins; frequent recurrence 

 after extirpation; extension of the disease to other parts by metas- 

 tases, etc. 



(29) The disease is one which progresses slowly, stunting the plant 

 first and finally destroying it, unless removed by extirpation or by 

 the development of increased resistance on the part of the plant. 



(30) The continuation of rigid State inspection with rejection of 

 diseased nursery stock is recommended. 



(31) The organism is moderately susceptible to germicides but can 

 not be reached in the galls. Moreover, germicidal treatment, after 

 excision of the galls (p. 184), can not be depended upon in all cases 

 because of the tendency of the organism to form metastases. 



(32) The organism from the daisy loses virulence on culture media, 

 and in some cases is believed to lose it also in the tumor itself (daisy, 

 hop, sugar beet). 



(33) The organism is believed to occur inside the rapidly prolifer- 

 ating cells, which by its presence are stimulated to divide with 

 formation of the tumor. 



(34) During the progress of our studies a new disease of the sugar 

 beet has been discovered. This disease, which is liable to be confused 

 with crown-gall, causes overgrowths of a coarse nodular nature which 

 soon disintegrate. It appears to be a more serious enemy to the 

 sugar beet than crown-gall, and is one to be greatly feared should it 

 become generally disseminated. We have called it tuberculosis of the 

 beet, and have designated the yellow organism causing it Bacterium 

 heticolum n. sp. (p. 194). 



213 



