Bacteria 
These living glows must not be confused with the 
strange little flashing lights sometimes seen on the 
tuberose in India, especially on very hot evenings. 
This has not yet been explained, but seems to be due 
to electric flashes. 
Spontaneous combustion, such as may happen to hay 
and straw when stored in too wet a condition, is the 
work of certain bacteria. On such damp grass stems 
huge quantities of micro-organisms begin to grow and 
are supplied by the organic matter diffusing out of the 
hay. All these germs as well as any cells still alive in 
the hay are actively breathing, taking in oxygen and 
giving out carbonic acid.® Any heat produced is 
retained, and the temperature gradually rises until the 
whole stack bursts into flame. This is a special danger 
on board ships laden with cargoes of cotton and other 
vegetable matter. One of the bacilli lives at tempera- 
tures of 50° to 60° C., and its spores can resist a heat 
of ro0° C, 
Besides light and heat, beautiful colours and strong 
perfumes are often due to bacterial workings. Some 
of these latter scents remind one of ripe strawberries ; 
the “marigold” smell of African rivers described by 
Mr. Kipling is also a bacterial bougued, 
The colours are often quite vivid and beautiful. 
There are several rich reds and pinks, of which the 
crimson Micrococcus prodigiosus, with its extraordinary 
resemblance to freshly shed blood, is the most interest- 
ing. This is often to be seen on bread and other 
provisions. Milk may become a deep blue, and there 
are also light blues and purples and yellows ; a beauti- 
ful fluorescent colour is formed by Bacillus lactis 
aerogeneus.’ Glue may be turned into a deep black 
colour. 
Perhaps the prettiest of all is the rich golden russet 
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