THE ORIGIN OF THE PLANT TUMOR CELL 



617 



Figure 2. Three stages in the recovery of a crown-gall teratoma. E. A tumor bud, 

 such as is shown at the top of the teratoma pictured in Figure 1, D, was grafted to 

 the cut stem tip of a normal tobacco plant. Note the abnormal character of the re- 

 sulting growth. F. A tumor shoot of the type shown at the apex of E was grafted 

 to the cut stem end of a healthy tobacco plant. Note that the resulting growth ap- 

 peared more noiTnal than that shown in E. Although the lower portion of the scion 

 showed evidence of abnormal growth behavior, the upper portion appeared normal, 

 flowered, and set seed. G. Seed from a recovered scion, such as that found in F, 

 was planted and upon germination gave rise to normal tobacco plants of the type 

 shown. Since the normal tobacco plant shown in G was derived from teratoma tissue 

 of single-cell origin (Figure 1, C), the results demonstrated unequivocally that the 

 progeny of a single somatic cell of tobacco may possess all of the potentialities neces- 

 sary to reconstitute an entire tobacco plant. 



return to normality of such cells could be achieved if conditions could 

 be defined that would permit the controlled manipulation of these 

 alternative areas of cellular metabolism. 



References 



Black, L. M., 1949. "Virus Tumors," Surv. of Biol. Prog. 1, 155. 



Black, L. M., 1951. "Hereditary Variation in the Reaction of Sweet Clover to the 



Wound-Tumor Virus," Ai7i. J. Bat. 38, 256. 

 Brakke, M. K., Vatter, A. E., and Black, L. M., 1954. "Size and Shape of 



Wound-Tumor Virus," in Abnormal and Pathological Plant Growtli, Brook- 



