SLIME-FORMING BACTERIA. 



149 



no case be proved. Consequently, the analogy formerly 

 assumed to exist between this fungus and the algae genus 

 Nostoc (implied in the name Leuconostoc) falls through. 



Under certain conditions the cells are surrounded by a 

 strong gelatinous sheath with a sharp outline (Bb, Be, C), 

 which in many of the above consists of a mucilaginous carbo- 

 hydrate, dextran. This formation only takes place in the 



Ba. 



*t ! 



Fig. %7.Leuconogtoc megenterioideg, Cienkowski (after Zopf). A, Cell cluster of the sheath- 

 less variety, taken from a potato cultivation ; B, series showing the development of a culture, 

 grown in gelatine, free from sugar ; Ba, sheathless ; Bb, the same after 24 hours' growth in 

 a solution of molasses, sheaths already seen but not strongly developed ; Be, after 48 hours' 

 growth in molasses, the sheaths strongly developed and partly encased in each other; C, a 

 small gelatinous mass from which the cells have been expelled. 



presence of cane and grape-sugar, and not in solutions of milk- 

 sugar, maltose, or dextrin. Under the latter conditions, and 

 in potato cultures, the species develop distinctive forms, in 

 which the gelatinous sheath is completely absent (A, Ba). 

 The formation of jelly is a phenomenon depending also upon 

 certain conditions of nutriment. 



Leuconostoc ferments grape-sugar, cane-sugar (after previous 



