Micro-organisms oi? Maple Sap : i:'>7 



common forms may be found growing together in association. In 

 addition to various common saprophytic bacteria, wild yeasts of 

 several types, and green molds of the genera Penicillium and 

 Knrotium arc frequently met with, particularly towards the cl< 

 of the season when the temperature becomes more favorable 

 for their development. Green sap. for example, is associated 

 with the presence of a group of bacteria characterized by green 

 fluorescence and does not appear to be caused by the swelling 

 of the buds to which it is so frequently related in time, hi one 

 type of stringy sap occasionally found, the only significant or- 

 ganism was one described in this paper as Bacillus a ecu's { new 

 Species), while in another type of stringy sap common at the 

 close of the season, several species of bacteria, various wild 

 yeasts, and molds of different genera occurred in association. 

 Gray and red yeasts are commonly associated with bacteria in 

 so-called red sap. Spore-bearing bacteria of the hay bacillus 

 type were frequent in certain samples of milky sap examined. 

 while the condition of other samples seemed attributable to the 

 collective action of many different organisms. 



The conclusion stated in the preliminary publication, that 

 there is a causal relation between micro-organisms and sour 

 sap and the resulting poor sirup, has been confirmed by all the 

 examinations made during the progress of the work, and by the 

 inoculation experiments to be reported later. A sequence of 

 species was noted during the season of 1909, and discussed on 

 page 494 of bulletin 151 where the following sentences occur: 

 "The predominating organisms found during the early days of 

 the sugar season belong to the yeast-like group, while bacteria 

 were relatively few in numbers. As the season advanced these 

 conditions were reversed." Subsequent studies have not con- 

 firmed this observation. For the past two years relatively few 

 organisms of any kind have appeared on the plates early in 

 the season, but as a rule bacteria have predominated, anjd in 

 general yeast-like organisms have appeared in important num- 

 bers only after the season was well advanced. 



