Il6 MAINE AGRICULTURAL EXPERIMENT STATION. 



branched into T or Y shaped bodies, it was impossible to deter- 

 mine whether they were true bacteria. They were therefore 

 called by the discoverer bacteroids. This contribution marks 

 the beginning of serious investigation as to the nature and etiol- 

 ogy of the tubercles. 



A few years later, Erickson* found that in the early stages of 

 the tubercles, long branching threads, like the mycelium of 

 fungi, were present but he was unable to determine whether 

 there was any connection between these and the bacteroids 

 which appeared later. 



Other experimenters a little later concluded, as already indi- 

 cated, that the tubercles were normal parts of the plant and had 

 no connection with infection from without. The bacteroids 

 were observed but were not considered distinct organisms. 

 They were considered rather as differentiated portions of the 

 proteid contents of the cells which were later absorbed by the 

 plant. This was the view of Brunchorst;f also of Sorauer,! 

 Van Tieghem and Duliot^j and others. 



In 1887, Marshall Ward proved conclusively§ that the tuber- 

 cles are caused by some organism which is abundant in the soil, 

 apparently a parasitic fungus. 



In 1888, Beyerinck§§ undertook the cultivation of the organ- 

 ism in artificial media and was confident he could trace the 

 development of the bacteroids from a bacterium which he named 

 Bacillus radicicola. The bacteroids were regarded as degenerate 

 forms appearing only after the bacteria had lost their vigor. 



In 1890, Prazmowski published the results of extended 

 researches,** the results of which are so concisely summarized 

 by Connff in the Experiment Station Record, that I take the 

 liberty of quoting freely in this connection. 



According to the investigations of Prazmowski the develop- 

 ment and growth of the tubercles are as follows: Bacterium 

 radicicola lives normally in the earth and collects in numbers on 



*Stuclier Sfver Leguminosernas Rotknoler Lund, 1874; Bot. Zeitung 1874, p. 381. 



fBer.d. Deutscu. Bot. Gesell. Ill (1885), pp.241, 257. 



JBot. Centralb. XXXI, (1887), 308. 



ITBull. d. Soc. Bot. France, XXXV (1S8S). 



§Phil. Trans. Roy. Soc. CLXXVIII 0887), 139-562. 



§§Bot. Zeitung. Bd. 46, (1888), p. 725 et seq. 



**Landw. Versuch. Stationen, 37, p. 161. 



tfExpt. Sta. Record II, 689, (1891). 



