Studii;s on Crown Gall of Plants 409 



the German colonies, were at this meeting, and Smith interviewed 

 them both in their work rooms a few days later. He also chatted 

 for a half hour or more at the Dahlem school for gardeners with 

 Dr. Carl Miller who served as secretary of the meeting. He called 

 on Dr. Oskar Brefeld but the aging and almost blind German 

 scholar was not at home. During his homeward journey, he 

 received a letter from Dr. Karl Goebel who wrote to thank him 

 for a copy of his " magnificent book " on bacterial plant diseases. 

 Berlin had been a veritable feast of science. 



On the morning of July \C\ Smith left Berlin to go by way of 

 Hannover and Essen t© Utrecht, the Netherlands, where he arrived 

 that night. There he saw the botanic garden, and immediately 

 went on to Amsterdam. Since 1902 when he had entertained in 

 Washington Dr. F. A. F. C. Went, professor of botany in the 

 University of Utrecht, he had been invited to visit there, and 

 had written the professor of his plans to be in Europe this year. 

 Dr. Went, however, was in the Hague for two weeks and had 

 not been able to reach Smith by letter to arrange a later time for 

 the visit. Smith spent many days at Amsterdam, Haarlem, Hille- 

 gom, Leiden, and other places of interest. At the University of 

 Amsterdam he visited the laboratory of Dr. Hugo de Vries. At 

 Haarlem and Hillegom he collected diseased bulbs of hyacinth 

 yellows, dissected them, and confirmed his earlier work. Ob- 

 serving that in some growers' bulb catalogues varieties were 

 designated as susceptible or resistant to the disease, he discussed 

 with them the matter of varietal resistance and how, if at all, 

 disease-resistant varieties could be obtained by hybridization.^ A 

 " glorious display of hybrid Gloxinias " and a " good collection of 

 single and double, extraordinarily large-flowered tuberous-rooted 

 Begonias," obtained by crossing and selection, were among the 

 many floral displays he examined. But his most important study 

 began when he started bacterial cultures at the Phytopathologisch 

 Laboratorium of the Willie Commelin Scholten of Amsterdam, 



'In his Bacteria in relation to plant diseases 2: 95-96, Smith recommended sys- 

 tematic cross-breeding experiments in many pLints for resistance to bacterial disease: 

 " These should be taken up as a part of the regular work of Departments of Agri- 

 culture and Experiment Stations and carried on without interruption for a long series 

 of years — long enough to insure good hybrids of fixed quality. In some cases 

 systematic selection within the limits of susceptible varieties might lead to useful 

 results." Practically the same as this statement was written into his diary at this time. 



