596 Third European Journey 



another photograph of a " Tumor formation in Bryophyllum." 

 This was also a frontispiece, and was published to show that " one 

 successful crowngall inoculation on Bryophylhnn calycmmn does 

 not protect from a second inoculation." His explanation read: 



The base of the plant was inoculated with the hop strain of Bacterium 

 tumejaciens March 22, 1920. The top of the plant was inoculated with 

 the same strain of the organism on October 3, 1921, after the lower tumor 

 had become of large size. Photographed March 2, 1922, about one-third 

 natural size, i. e., the height of the plant was 20 inches. At this date both 

 tumors were still free from necrosis, the lower tumor being nearly two 

 years old and the upper one over five months. 



Smith's two most important publications of this period were 

 communicated in 1924 and 1926 to the National Academy of 

 Sciences: the first,, " Tumors, cysts, pith bundles, and floral pro- 

 liferations in Helianthus," '' and the second, an abstract of which 

 was published also in Science,''^ " Changes of structure due to a 

 modified environment. A study of labile protoplasm in Helianthus 

 anmius L." Following his discovery in 1923 of four sunflower 

 heads with strop-shaped flowers located in the middle of the head 

 and among tubular disk flowers, he found on July 25, 1924, 

 "" tumor strands " in the pith of sunflowers inoculated twenty-two 

 days previously. He fixed one in carnoy for sections, and this, 

 when examined on August 29, was seen to be " a perfect vascular 

 cylinder in the center of the pith and in its center [were] tumor 

 cells." Immediately he wanted to know whether these phenomena 

 could be obtained by simple woundings and in the absence of 

 tumor irritation. He had studied the effects of simple wounds on 

 other plants. On about sixty undeveloped sunflower heads, he 

 punched out the middle of the torus, but three ^^ weeks later he 

 examined them in blossom and could find " no evidence of any 

 central strop-shaped flowers." Believing that '" the woundings and 

 inoculations " had not been made early enough, he decided to 

 repeat the experiments the next year. 



From the beginning of his study of these phenomena, it appears, 

 he attributed their occurrence to some " mechanical traumatic 



^«Mew. Nafl Acad. Sci. 22(4): 1-50, 43 pi., 1924. 

 *' 63(1637): 505, May 14, 1926. 



^* Twenty-five days for one set. Eleven days for another. Diary, Aug. 18, for 

 conclusions. 



