432 



BACTEEIAL DISEASES OF PLANTS 



(with difficulty), Juglans, poplar, Pterocarya, Allemanda, mango, 

 stock, Ricinus, cassava, Fuchsia, Reseda, Salvia, Pisum, Calen- 

 dula, Helianthus, etc. 



Technic. The writer and his associates experienced great 

 difficulty in first isolating this organism from crown galls but 

 now that the obstacles are known they are easy to evercome and 

 any one with ordinary technical ability can demonstrate the 



FIG. 330. Crown gall on white Paris daisy (Chrysanthemum frutescens). 

 Plant inoculated December 13, 1906, with a pure culture of Bacterium tumefaciens 

 (plated from a tumor on the daisy) and photographed 7 months later. One branch 

 killed. }'4 natural size, circa. 



occurrence of the parasite in sound galls by the poured-plate 

 method, with exception of certain problematic galls occurring 

 on the sugar beet. The organism is best isolated from young and 

 rapidly growing tumors, from which it may sometimes be had in 

 practically pure culture. Old galls are apt to be filled with white 

 and variously colored non-parasitic schizomycetes, especially 

 with yellow and white ones, and may contain mites, nematodes, 

 yeasts, myxomycetes, and various fungi. 



