226 Barker . — A Fragrant c My coderma ’ Yeast , 
clearly made out, but during the swelling of the spore it 
becomes much less noticeable. Whether it is a fold which 
stretches out as the wall extends, or a solid rim the substance 
of which swells and is used up, could not be determined. 
The buds are developed, not only on the rounded surface of 
the spore, but also on the flattened base, as seen in Fig. n, 
so that the spore eventually loses to a great extent its 
hat-like shape. 
It may be noticed as a point of interest that there is no 
preliminary mycelium nor any structure analogous to a pro¬ 
mycelium developed during germination, typical Yeast-cells 
being formed at the first budding. 
Physiology. 
Temperature limits . The optimum temperature of growth, 
as judged by the amount of development in streak-cultures 
on beer-wort agar-agar, is 28° C. Growth is possible at all 
temperatures between i5°C. and 3 2° C. At to°C. it is very 
slow, while exposure for five minutes to a temperature of 55 0 C- 
kills all, or nearly all the vegetative cells. Exposure for the 
same period to a temperature of 50° C., however, leaves many 
cells still living. 
Aerobism. Complete absence of free oxygen prevents 
growth, or at any rate prevents its initiation, but the presence 
of mere traces of that gas will allow growth to continue. 
Thus, if a flask of beer-wort infected with the Yeast be 
exhausted by the filter-pump for two hours, or even when 
the filter-pump is allowed to act continuously, the character¬ 
istic film is slowly formed on the surface of the liquid. If 
a series of plate-cultures be made, using beer-wort gelatine 
as the medium., and placed under the same conditions, 
colonies of the usual form are developed. This is probably 
owing to the impossibility of removing all the air by such 
means, because if the above experiments are performed in the 
presence of a solution of pyrogallic acid in caustic soda, in 
neither case is there a development of the Yeast. 
Similar results are obtained if the inoculated flask is placed 
