EARLY PROBLEMS 15 



Doctors Mary Lojkin and Vinson found that trypsin and pancreatin in- 

 activated purified tobacco virus but did not do so in the crude leaf extract. 

 Emulsin, pepsin, and yeast extract showed no effect on the purified virus, 

 except pepsin after many days' incubation. The work of Vinson and his 

 associates laid the foundation for the later epochal work that Dr. W. L. 

 Stanley did at Rockefeller Institute in purifying tobacco mosaic and iden- 

 tifying it as a large protein molecule. C. N. Priode, M. W. Woods, H. H. 

 Thornberry, and others also worked with Dr. Kunkel on virus diseases 

 while he was at the Institute during the ten years from 1923 to 1932. 



During the decade Dr. Kunkel and his associates had made the Institute 

 outstanding headquarters for contributions to the knowledge on virus and 

 yellows diseases of plants. Rockefeller Institute for Medical Research, in- 

 cluding the branch at Princeton, were, of course, interested in virus diseases 

 as well as other diseases of both humans and animals. They concluded that 

 researches on human, animal, and plant diseases could be carried on profit- 

 ably in close association, the advance in each contributing to and benefiting 

 by advances in the others. This is especially true of virus diseases. Conse- 

 quently, Rockefeller Institute employed Dr. Kunkel to head a new division 

 of plant pathology at Princeton, New Jersey, as a part of their now newly 

 named Department of Animal and Plant Pathology. Dr. Kunkel planned 

 and built at Princeton a fine modernly equipped plant pathology laboratory 

 and manned it with scientists well trained for handling the several phases 

 of plant pathology, especially virus and yellows diseases. He took with him 

 three scientists who had formerly worked at the Institute. Following the 

 policy of avoiding duplication of phases of plant science already strong in 

 northeastern United States, the Institute did not attempt to reorganize and 

 re-man the virus disease project. Some of the scientists on the project at 

 the Institute shifted their efforts to other projects, but Dr. Beale and asso- 

 ciates !• 2. 10 have continued to date with their work on the serum reaction 

 of plant viruses and other phases of the problem. 



A Duck Food Problem 



The work on the duck food problem described below was carried out by 

 Dr. W. S. Bourn with advice and help of the scientific staff of the Institute. 

 Bourn defines the problem, its support, and execution in essentially the 

 following language.' • p-*" 



The inland waters of North Bay and Back Bay in Virginia and Currituck 

 Sound in North Carolina have long been known to be one of the most im- 

 portant winter feeding grounds for migratory wild fowl in the United States. 

 In these waters there formerly thrived in great abundance such submerged 

 angiosperms as Potamogeton pectinatus L. (sago pond weed), P. perfoliatus L. 

 (redhead grass), P.foliosus Raf., Naias flexilis (Willd.) Rostk. & Schmidt, 

 Vallisneria spiralis L. (wild celery), Ruppia niaritima L., and Ceratophyllum 

 demersum L., all being valuable food plants, according to McAtee, for wild 



