LAsr WoKK. Final Honors 599 



and i;iviiii^ otT tumors at intervals, (3) the pith stems have reversed bundles 

 i.e. phloem in the center and xylem on the periphery, (4) occasionally 

 roots developed in the center of the ilowcr head, (*)) in a few cases com- 

 plete secondary small capitula formed in the head as a rose sometimes 

 proliferates out of a rose, most of these were sessile but four of them were 

 pedicellate, (6) the development of bii^ leafy bracts and expanded yellow 

 ray flowers in the middle of the disk flowers was often very striking. 



He planned to repeat on a large scale some experiments to 

 decide whether by wounding very young buds he could not get 

 the same results as to proliferation without using the crown gall 

 organism. Already he had about one hundred wounded side 

 flowers on big plants and these, together with seedlings coming 

 on for autumn, would provide, he thought, sufficient material. On 

 August 1 1 he counted one hundred and fifty-seven wounded sun- 

 flower heads and, finding not a proliferation, cyst, or abnormal 

 development of vascular bundles in the pith, he concluded, 

 " Woundings without crowngali inoculation will not cause green 

 bracts and ray flowers." But by September 28 his conclusion was 

 changed: "All but 5 of the 108 needle pricked sunflower heads 

 are now in blossom," he wrote. " 3 of the youngest heads (of 

 those in bloom) show ray flowers (not yet open) among the 

 tubular flowers. Wounding alone will cio it! If done early 

 enough." He now had enough material for " an interesting 

 paper " and the general conclusion he drew from the experiments 

 was that "many of the common teratological forms in plants and 

 animals are due to parasitic or mechanical traumatic displacement 

 occurring in early life." More specifically, he said: 



The results of these experiments confirm and extend earlier ones on 

 other plants — daisy, pelargonium, sugar beet, tobacco, ricinus, tropaeolum, 

 etc. They show that what young cells will become depends to a very con- 

 siderable extent on how they are treated. A changed stimulus, if not 

 too strong and if applied early enough, leads inevitably to a changed 

 structure." -•'^ 



While his experiments on sunflower plants were being pursued, 

 he had been studying also crown gall inoculated Ricinus plants. 

 In the first weeks of August 1924, three of his diary memoranda 

 read: 



^^ Tumors, cysts, pith bundles, and floral proliferations in Hclianthus, op. cit., 

 summary and discussion. 



