318 EXPERIMENT STATION RECORD. 



ditions (weather, soil, manuring, etc.) are able to bring the disease 

 germ from the latent stage to the visible mycelium and (2) on the 

 supply of new infectious material from without. — F. w. woll. 



The micro-organisms of the tubercles on the roots of leguminous 

 plants, M. Maze (Ann. Inst. Pasteur, 12 (1898), No. 1, pp. 1-25; 2, pp. 

 128-155, pis. 2, fig. 1). — The author reports an extended investigation 

 of the physiology and morphology of the organism which causes the 

 development of tubercles on the roots of leguminous plants and through 

 which the assimilation of atmospheric nitrogen takes place. 



In his general conclusions he states that the free micro-organisms in 

 the soil are attracted toward the roots of leguminous plants by the 

 intervention of carbohydrates diffused in the soil in the vicinity of the 

 root hairs. The organisms penetrate the tissues and cause the forma- 

 tion of a nieristematic growth which gives rise to the tubercles. Before 

 the tubercles are formed the organisms are engulfed in a glutinous body 

 which has somewhat the aspect of a mycelium. Later, by the circula- 

 tion of the saj) of the plant into the tubercles, this glutinous material 

 is carried throughout all parts of the plant, and the bacteria are also 

 exposed to the action of the acids dissolved in the plant juices. The 

 pseudo-mycelium does not constitute a part of the living organism. 

 Investigation has failed to show the presence of the organism in this 

 mycelium by any of the means adopted. .By the time the plant is 

 matured the tubercles are deprived of their nutrition and the bacteria 

 issue from the tubercles in the form of a bacillus endowed with new 

 properties and capable of living free in the soil. 



The fixation of free nitrogen can be brought about in artificial cul- 

 tures as well as in the root tubercles. The author found that the 

 addition of saccharose to various culture media and the thorough 

 aeration of the medium admitted a growth of the organism that was 

 capable of fixing the free nitrogen. The proportion between the amount 

 of nitrogen fixed and the saccharose furnished to the organism was 

 somewhat constant. When 2 per cent was added to the medium, a 

 little more than double the amount of nitrogen was fixed than when 

 only 1 per cent was used. All the forms which are found in nature 

 may be reproduced in artificial media by the action of heat, acid, 

 peptonized media, etc. 



The bacteria recently isolated from the tubercles retain for some time 

 their ability to reproduce new tubercles by inoculation. The forms 

 differentiated during the saprophytic life are gradually lost. The 

 author states' that the saprophytic forms in the soil are undoubtedly 

 able to establish themselves on roots and form tubercles, but that he 

 has so far been unable to isolate them from the soil. The independent 

 forms of the root tubercle organism are said to represent a state of dis- 

 sociation; the first a bacterium which bears endogenous spores; the 

 other an Oospora which bears conidia. The last state is usually borne 

 upon the surface of the soil. The bacteria spread during the winter 



