BUREAU OF PLANT INDUSTRY. 281 



LABORATORY OF PLANT PATHOLOGY. 



The general laboratory and research work in plant pathology has 

 continued under the immediate direction of Dr. Erwin F. Smith, 

 Pathologist. Several lines of investigation which have been carried 

 on in the laboratory for periods ranging from one to several j^ears 

 have been completed and the results prepared for publication in bulle- 

 tin form. 



Bud-rot of the coconut palm. — The study of the bud-rot of the 

 coconut palm has been continued and its cause has been determined. 

 Extensive experiments have been carried on with a view to its preven- 

 tion and eradication. The results of several years' work are now in 

 manuscript and will be submitted for publication at an early date. 



Destructia-e Tu:iroR disease of limes and other citrus fruits. — • 

 A study has been made of a destructive tumor disease which has been 

 shown to be of fungous origin and to attack not only limes, on which it 

 was first observed, but also oranges, while artificial infections have 

 been produced on the pomelo, lemon, and Citrus trifoliata. The fun- 

 gus spreads far beyond the original point of infection, and this must 

 be borne in mind in pruning for purposes of eradication, as mycelium 

 has been traced in the stem from 1 to 2 feet beyond any external sign 

 of infection. A bulletin containing the results of the investigation is 

 ready for publication. 



Crown-gall of plants. — The study of crown-gall has been con- 

 tinued in cooperation with Dr. C. O. Townsend, formerly of this 

 Bureau, and Miss Nellie A. Brown, of the Office of Sugar-Plant 

 Investigations. The crown-gall of cultivated plants has been shown 

 to be cross-inoculable to an astonishing degree. Galls have been pro- 

 duced on various species belonging to widely different families by 

 pure culture inoculations with Bacterium tumefaciens isolated from 

 the Paris daisy. This organism has been inoculated many times suc- 

 cessfull}^ into the peach, rose, hop, sugar beet, white poplar, and 

 other susceptible plants. That from the crown-gall of the peach has 

 been many times inoculated into the Paris daisy, sugar beet, hop, and 

 other plants. Successful cross-inoculations have also been obtained 

 with the organisms isolated from the crown-galls of many other 

 plants, among them apples infected with hairv-root, the cause of 

 which has so long been a matter of conjecture and dispute. A bulle- 

 tin containing a detailed account of these researches has been pre- 

 pared for publication. 



New spot disease of cauliflower. — Considerable attention has 

 been given during the past year to a new disease of caulitlower. The 

 cause has been determined, a biological study of the parasite has been 

 made, and many experiments have been carried on to determine the 

 conditions under which infection takes place. A bulletin concerning 

 the disease is ready for publication. 



Cooperative studies of plant diseases. — In addition to the gen- 

 eral laboratory work, studies are being made of the bactenal and 

 fungous content of spoiled maize, biochemical studies of pure cultures 

 having been undertaken by Dr. Carl L. Alsberg, of the Office of Drug- 

 Plant Investigations. In cooperation with the Office of Sugar-Plant 

 Investigations studies are being made of the interrelation of crown- 



