THE CROWN GALL: TECHNIC 449 



likewise, soft shoots of young tobacco or the undeveloped disks rV^f) 

 of the sunflower. For study of the leafy tumors (teratomas), 

 inoculations may be made in the leaf axils or on the cut inter- 

 nodes of various plants. The writer has used chiefly tobaccos 

 and the common hothouse Pelargonium. In the same way, 

 for tumors containing roots, the tops of I?npatiens balsamina 

 (the common garden balsam) may be inoculated. For study 

 of the tumor-strand and secondary tumors, the young rapidly 

 growing shoots of the Paris daisy (Chrysanthemum frutescens) 

 are best, and the inoculations should be made toward the top 

 of succulent stems which should continue to grow vigorously 

 for at least 2 months. The needle should be thrust into the 

 stems immediately under the leaves. Peklo in Bohemia 

 (1915, 1. c.) obtained very good tumor-strands in the stem of 

 the sunflower by inoculating into the young flower disk, and the 

 writer has verified his statements. Hop does not infect daisy. 



The result of the inoculations will be successful and inter- 

 esting in proportion to the virulence of the organism and the 

 activity of the plant. Well nourished rapid-growing plants 

 yield much larger tumors than slow-growing ones. To demon- 

 strate killing effects of the gall use young sugar beets or young 

 Nicotiana sylvestris, inoculating in the center of the crown. 



Cuttings of the Paris daisy, if made in the hothouse in 

 September, should give plants suitable for inoculation in 

 November and December. The slips should be end branches 



FIG. 342. Crown-gall teratoma on orange due to Bacterium tumefaciens- 

 Stem inoculated January 14, 1916. This is my No. 48 (hop strain through sun- 

 flower, colony 1). It was made by needle pricks in the region of a dormant bud, 

 but nothing in the way of a tumor developed either in 1916 or 1917. I looked 

 at it many times. Other inoculated orange buds developed slight tumors bearing 

 supernumerary buds and then died. The small firm dark green shoot marked X 

 is an outgrowth of the stem. This appeared in 1917 but with no evidence of 

 any tumor at its base. Three other shoots and about 12 buds developed from the 

 tumor itself and all of them were soft and light green. This young, rapidly growing 

 tumor appeared within 3 or 4 weeks of the time the photograph was made. The 

 tumor is interesting as having remained dormant for two years and then begun 

 to grow rapidly as an embryoma. The rough white part of the tumor is the 

 naked sarcoma. Photographed March 2, 1918. X 3. Sections of leaf C and of 

 shoot y between a and b were cut and examined for a tumor-strand but none was 

 found. 



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