286 STATE BOARD OF AGRICULTURE. 



Some minor differences exist, however, that can be detected only when a com- 

 parative examination is made. Those from the clovers are very similar, as are 

 those of the cowpea and soy bean. Slight differences exist, however, between 

 the colonies from these two classes. 



After the organism is once isolated to artificial media, it is desirable to main- 

 tain and increase its vitality, if possible. To attain this end in our work, the 

 organism was transferred to slant agar tubes of peptone-free media, and grown 

 at a temperature of 25°C. for 48 hours. The tubes were then removed to a tem- 

 perature of 16°-1S°C. and allowed to remain. Under these conditions the culture 

 remains fresh and actively vital for a much longer time than if grown in media 

 rich in nitrogen at a higher temperature. 



Associated with the old cultures grown as indicated above, we find the large 

 rod and branched forms. The branched forms are peculiarly branching micro- 

 organisms resembling the letters "T," "X," and "Y." In our investigations we 

 have found these forms in old cultures only, and on media deficient in and entirely 

 devoid of nitrogen. Their presence was demonstrated by making a series of stains 

 from 1-15 and 30 day cultures, respectively. The 24-hour culture possessed the 

 minute rod forms only. In the 15-day culture, several of the large rod and 

 branched forms were present, with the minute rod forms in the majority. In the 

 30-day culture, the large rod and branched forms were quite numerous. 



According to Moore, the assimilation of atmospheric nitrogen is attributed to 

 the large rod forms which eventually become transformed into the branched 

 forms, and in the nodule the branched forms only can be acted upon by the plant 

 juices. Because of the close relationship between the occurrence of the large 

 rod forms and branched forms, as demonstrated by our own work, it is ques- 

 tionable whether any distinct line can be drawn between the nitrogen-assimilating 

 power of these two forms. 



I have attempted to point out the requirements necessary for the successful 

 cultivation and study of the organism in question. Although the work with 

 this particular organism is in a very tentative stage, much is being done at 

 present to determine its true economic importance. For success in practical field 

 experiments, much depends upon the cultural manipulations in producing inocu- 

 lating material. At present this work is progressing successfully in our laboratory, 

 and we hope in the near future to say definitely what can be done with this 

 organism nature has so fitly supplied to benefit leguminous plants. 



Laboratory of Bacteriology and Hygiene, June 29, 1905. 



