Mason: The Yeast- Fungi in Nature. 15 
with several instances in Yorkshire which have furnished 
exceedingly interesting material for study, one of which may 
be related. 
In the Winter of 1904 I found at Adel, near Leeds, a Birch tree 
' suffering very severely from the ravages of Polyporus betulinus, 
and that the disease was of long standing was evidenced by 
the prolific crop of sporophores. In the following spring I again 
visited the tree and found the work of its fungus foe completed. 
The top portion had been blown off, leaving a long oblique 
fracture, and the whole of the fractured surface upon the standing 
portion of the trunk was covered with a greyish-coloured slime, 
a patch certainly not smaller than two feet long by four or five 
inches wide. A small quantity of the substance was collected 
-and upon examination I was astonished to find’ that it 
consisted entirely of yeast-cells, which proved to be those of 
Saccharomycodes Ludwigit. Aiter preparing a pure culture of 
the yeast 1t was transferred - to agar medium in Freudenreich 
flasks and preserved for future observation. One oi these 
flasks remained unopened until 1911 when it was again ex- 
amined ; it was then found that most ot the cells had developed 
spores, but the culture still contained vigorous cells capable 
of budding. 
Two interesting points may be mentioned in connection 
with this occurrence of S. Ludwigit. The aggregations of this 
organism, poducing Slime-flux, are usually found upon the 
oak and have only occasionally been recorded as occurring 
upon other trees ; the present case is concerned with the birch. 
As a rule, the slimy exudations upon trees consist of a mixture 
of organisms such as Endomyces, Yeasts and Torulae, but 
here S. Ludwigit existed as a pure cuiture so far as it is possible 
for this condition to obtain under natural conditions. 
As will have been already gathered, the various species of 
yeasts cannot be determined by microscopical examination 
alone. The cells as found in nature must be isolated ; a pure 
culture prepared, grown in various nutrient media, and spore 
formation be induced. These operations demand a_ fair 
knowledge of microscopical technique and some experience 1n 
methods of pure culture, but not more than are required of 
the mycologist working at the micro-fungi in general and having 
the requisite skill to deterime specific differences amongst 
the members of various families, say of the Phycomycetes and 
Hyphomycetes. 
A species of yeast has been found upon Holly Berries ;* 
systematic examination of the various woodland fruits would 
doubtless reveal the presence of others, some probably new. 
There are two genera, each embracing but a single species 
* Sacharomyces tticis Grénland. 
1913 Jan. 1. 
