Peb. 
so, 1923 
Life History of Azotobacter 
415 
Table I .—Types of growth and transformations observed in strains of Azotobacter 
Number of transformations to different types of growth. 
Type of growth at beginning 
of experiment. 
1 
& 
y 
«* 
bfl 
U 
at 
•4 
Coccoids. 
Dwarfed growth. 
Spore-free 
small rods. 
Fungoid growth. 
Sporulat¬ 
ing rods. 
i 
1 
White. 
Yellow. 
•0 
& 
White. 
I 
Yellow. 
White. 
Yellow. 
Orange. 
Small. 
I 
Total. 
Large spore-free cells... 
x 
2 
2 
A 
A 
x 
0 
0 
1 
O 
tr 
7 
35 
Coccoids: 
*t 
*r 
V 
White. 
3 
1 
0 
i 
0 
7 
0 
i 0 
7 
I 
17 
Yellow. 
1 
2 
0 
0 
2 
O 
3 
0 
O 
O 
3 
I 
0 
O 
0 
12 
Red. 
1 
0 
0 
O 
0 
0 
0 
0 
0 
O 
0 
1 
Dwarfed growth. 
2 
1 
1 
0 
! 2 
3 
I 
6 
I 
I 
0 
18 
Spore-free small rods: 
White. 
4 
5 ; 
4 
0 
4 
0 
I 
X 
I 
2 
I 
23 
Yellow. 
0 ! 
0 
0 
0 
1 
O 
0 
2 
0 
O 
0 
3 
Fungoid growth: 
White. 
3 
5 
3 
0 
4 
5 
1 
1 
I 
3 
I 
27 
Yellow. 
0 
0 
0 
0 
0 
0 
1 
0 
0 
0 
0 
X 
Orange. 
0 
1 
0 
0 
1 
2 
0 
0 
X 
0 
I 
6 
Sporulating rods: 
Small. 
2 
3 
1 
1 
2 
2 
0 
4 
0 
I 
4 
20 
Large. 
5 
1 
4 
0 
4 
3 
0 
3 
0 
X 
4 
25 
Total. 
21 
19 
16 
3 
25 
24 
6 
21 
14 
6 
18 
IS 
188 
I.—LARGE NON-SPORULATING CELLS 
In another paper, published in 1908 by the senior author together 
with T. Westermann (jo), a detailed description was given of all pecu¬ 
liarities of the large Azotobacter cells, based on a comparative study of 
21 strains, to which only few additions are to be made. The observa¬ 
tions then made upon the tendency of Azotobacter to form branched 
threads and to grow occasionally as a yellow or as a white sarcina have 
now found their explanation in the discovery of the fungoid and of the 
coccoid types of growth. It was also pointed out in that report that in 
several respects, especially in its colony formation and in its growth on 
potato, Azotobacter may exhibit certain traits characteristic of sporulat- 
ing rods. Numerous confirmative results were obtained in this direction. 
Not infrequently the colonies on mannite-nitrate agar did not show the 
typical coarse dark gray granulation, but a more or less hairy and 
brownish structure, indicative of the tendency to develop the rod form. 
The change from whitish to yellowish to brown growth was seen with 
both Azotobacter chroococcum and A . Beijerinckii . In 1908 it was said 
that probably A. Beijerinckii should be classed as a variety of A . chroococ¬ 
cum; our new findings prove the correctness of this view. Expecially 
a white strain of A. chrooccoccum (No. 10), originally isolated by Praz- 
mowski (40), behaved exactly like A, Beijerinckii. And several typical 
strains of A. chroococcum kept for five years in mannite-nitrate solution 
assumed the same character—that is, they showed now little inclination 
to develop the typical dark brown to black color but produced a light 
yellow to light brown slimy growth. On the other hand, typical strains 
