Micro-organisms ok Maple Sap 



develops. Such sap is popularly called sour, and several typ 



arc recognized among which the most common is the so-called 

 green sap. In all the samples of greenish or greenish-brown sap 

 examined, the predominating organisms were of the fluoresced 

 type, and inoculation experiments have repeatedly demonstrated 

 their causal relationship to this type of spoiled sap. 



The initial infection of the sap is doubtless brought in from 

 the hark of the tree, by wind, and by dripping rain and snow- 

 water. Falling snow and rain also probably bring in some in i 

 (ion from the air. Fluorescent bacteria were demonstrated on the 

 tree bark as well as in the snow and surface water and in un- 

 washed buckets and spouts from the previous season. Lai 

 numbers of the organisms remain in the spout and buckets from 

 season to season, unless these are thoroughly cleansed by boiling 



Such maple sap organisms of the fluorescent type as have 

 been previously reported upon (4:492) were recognized as mem- 

 bers of the Pseudomonas group of Migula and more or less closely 

 related to Pseudomonas fluorescens. Both the liquefying and 

 non-liquefying types were observed. 



On account of the prevalence of this type of bacteria in 

 maple sap and their importance in the maple sirup industry, a 

 critical study of the characters of the group was considered im 

 portant. The discussion falls naturally under two heads: 



(1) A preliminary investigation with 42 strains of green 

 fluorescent sap bacteria. 



(2) A more exhaustive comparative study of seven repre- 

 sentative strains selected in the preliminary work and of six 

 known species. 



PrELimin \ry Studies TIVon 42 Strains of" Green Fi,i ori i int 



Sap Bacteria 



isolation 



The 42 strains of green fluorescent sap bacteria were selected 

 from several hundred cultures isolated from abnormal maple sap 

 secured in different parts of Vermont during four successive 



