THE FISSION FUNGI 493 
organic material is termed a saprophyte,t and when the 
chemical changes induced by its activity are offensive the 
process is putrefaction.? 
The motile rods multiply rapidly so long as there is any 
food available or until the putrid products become so concen- 
trated as to be harmful to the plant. Then the plants rise 
to the surface of the liquid, lose their swimming organs, 
form long threads by remaining attached end to end after 
fission, and at the same time they secrete a gelatinous covering 
which binds them all together into a rather firm layer or 
scum (A). While in this stage resistent resting spores are 
formed in many of the cells, by the protoplast becoming round 
and secreting a new cell-wall (C). If the liquid is allowed to 
a - = bs 4 
a ne .) - a 
oo” {e= 4 
Ge e - a - 
te ®e ‘ ‘ ute 4 e 
aw te .rt yg of = 
4 ‘ e 
4 a : a om) oe 
44 ‘ ay‘? Owe 
« on 8 ahah id 
4 oe * ate 
® -- 
Fic. 323.—Milk-souring bacterium (Bacterium acidi lactici, Rod-germ 
Family, Bacteriacew). Plants stained, 499%. (Migula.)—Causes the 
souring of milk by converting the milk-sugar into lactic acid. 
evaporate and the scum to dry it will become more or less 
powdery, and slight currents of air may then carry away 
minute bits containing many of these excessively small spores 
which no mere drying can harm. Myriads of such spores are 
-floating about in the air around us. -When a Bacillus spore 
falls into any putrescible liquid it germinates by elongation 
of the protoplast and the development of swimming lashes, 
thus forming a motile rod like that already described. 
_ Very similar to Bacilli, both in structure and life-history, 
are the many forms of the genus Bacterium which differs 
from Bacillus mainly in lacking swimming organs. Bac- 
terium acidi lactici (Fig. 323) causes milk to sour by convert- 
1Sap’ro-phyte < Gr. sapros, rotten. 
2 Pu”’tre-fac’tion < L. putris, rotten; facere, make. 
