l82 



Journal of Agricultural Research voi. xvni, no. 4 



In later work the organism has been obtained with almost complete 

 suppression of the yellow species, which are, no doubt, surface organisms, 

 by dipping a piece of diseased tissue in 95 per cent alcohol for an instant, 

 immersing in mercuric chlorid (i to 1,000) for one minute, and then 

 rinsing through five or six sterile water blanks before macerating and 

 plating out. 



When exudation has been abundant and the tissue clean, successful 

 isolations have been also made by touching an exudate drop with a sterile 

 platinum needle and transferring directly to an agar slant. This method 

 has proved especially satisfactory when the exudate has been forced out 

 in a damp chamber from leaves artificially infected in the greenhouse, 



although isolations have been made from 

 field material in the same way. 



In the investigation of this disease a 

 number of strains of the causal organism 

 have been used in inoculation as well as 

 in cultural studies. One of these, des- 

 ignated A, which has proved especially 

 virulent in both greenhouse and field 

 experiments, has been studied inten- 

 sively and is presented as the type 

 strain. This isolation was made from a 

 leaf lesion in 191 7. Some of the other 

 isolations will be considered in a com- 

 parative way later in this paper. 



MORPHOLOGY 



^ . ■ , ■ ^ ^ The organism is a medium-sized rod 



Fig. I. — Bacterium glyctneum: r rom 72-hour ° 



growth on potato agar, stained by Duck- with rOUUdcd Cnds and OCCUrS USUally 



wall's method to show flageiia. X 2.000. gingly or in pairs. When stained from 

 2-day-old potato agar cultures with Ziehl's carbol fuchsin or gentian 

 violet, the cells average about 2.3JU long by i .2m wide. When stained with 

 Duckwall's flagellum stain the average measurement is about 3m by i.5At. 

 Both Zettnow's and Duckwall's flagellum stains have shown the organ- 

 ism to be motile by means of one to several polar flagella (fig. i). 

 No endospores or involution forms have been observed. Capsules were 

 not demonstrated when stains were made from potato or beef-peptone 

 agar cultures, but well-developed capsules were found present on blood 

 agar. Both Welch's and Hiss's methods of staining were used. Light 

 flocculent and sometimes membranous pellicles developed on the surface 

 of certain liquid media such as bouillons of favorable reactions, sugar 

 solutions, and on Fermi's and Uchinsky's solutions. The organism is 

 gram negative. 



