THE UNIVERSE OP LITTLE THINGS. 207 
growth there is life. Is it plant or animal life ? Its 
motions and method of gemmation would lead us to 
think that it is animal. But it has been found that 
the capsular covering of these oval bodies contains 
cellulose matter, which has been considered a charac¬ 
teristic of vegetables.* 
The yeast germ is therefore regarded as a plant. 
It has no chlorophyll, and hence it can not make its 
own food out of carbon dioxid and mineral matter. 
It is compelled to live on more highly organized food 
prepared by higher plants. Organic matter is its 
food, and fermentation continues as long as there is 
food for the organism to feed upon. 
Compressed yeast is a collection of yeast germs, 
which may be kept in a cool place for several daj^s. 
Sometimes quantities of the germs are put into the 
form of a cake and dried. In this form they may be 
kept several months. 
If we put a quantity of the germs where they can 
get but little or no nourishment, they begin to make 
out of their own substance small granular bodies 
which have about the same relation to the germ that 
a seed does to the plant. These are known as spores. 
They have much greater power of endurance, and 
under favorable conditions will produce the germs, 
as the seed produces the plant. 
Occasionally the housewife finds that her bread 
does not turn out well, although, so far as she could 
* It has recently been discovered that the covering of the squid 
also contains cellulose. 
