418 
Journal of Agricultural Research 
Vol. XXIII, No. 6 
substrates—that is, a thin, colorless slime appears on solid media, 
while milk is left unchanged, and in broth as well as in mannite-nitrate 
solution hardly any growth becomes noticeable- More frequently, 
however, a better development takes place after a while, and in all 
cases observed by us this better growth was characterized by a bright 
yellow coloration, with the exception of two cases where later a red 
pigment was produced. The microscopical aspect and the other cul¬ 
tural peculiarities were identical in both cases. As no such bacterial 
growth was fully described before, as far as we know, the necessary 
data may be given here. 
Morphology (Pl. 3). —Typical Y to globular, oval, wedge-shaped, or rodlike 
cells, single, in short chains, or often in clumps, after two to four weeks mostly small 
cocci, l /i to Yu. Changes to small rods, to coccoids, and especially to fungoid growth 
were frequently observed; occasionally also upgrowth from the symplasm to large 
spore-free and to large sporulating cells. 
Staining after Gram was mostly negative; only in some cases very small granules 
showed a positive reaction, while the rest of the cells remained negative. 
Motility was mostly absent, only when Gram-positive granules were present the 
cells developed motility by one polar flagellum. 
Conjunction was frequent, especially in two days old cultures on salt agar and in 
salt-broth. Zygospores were formed. 
Gonidia were produced after the cells had grown up to full size. 
Gonidangia of threadlike, clubbed, or globular shape, the latter equal to normal 
Azotobacter cells, were produced especially on potato agar, on potato, in milk, and 
in mannite-nitrate solution. Thin needlelike outgrowth was seen occasionally. 
Regenerative bodies of globular shape appeared, as a rule, after 2 to 3 weeks, 
especially on agar and on potato. 
Microcysts.—T he small globular or oval cells often became thick-walled and 
germinated later to small, pale, thin-walled ovals. 
Endospores. —Pale, small ovals were seen to transform themselves in toto to bright, 
heat-resistant bodies, which gave rise to typical sporulating rods. 
Symplasm. —Nearly always small as well as large cells developed from the symplasm, 
the former always and in much greater number in the thinner portions close to the 
edge, the latter in smaller number in the inner thicker parts. Filidia and sclerotia 
were also produced occasionally, the latter resembling those shown in figure 108 on 
Plate 9. 
Colonies. —On beef agar and on mannite-nitrate agar circular, % to 1 mm. in 
diameter, whitish to yellowish, with finely granular to flaky yellowish structure, 
edge white, smooth. Occasionally larger, more slimy, and more whitish colonies 
were formed (changing to small rod type), or larger yellow circular colonies (changing 
to coccoid growth), or yellow brownish colonies with somewhat irregular edge 
(changing to fungoid growth). On beef gelatine small yellow, dense colonies with 
smooth, sharp edges were formed; gelatine was not liquefied. 
Agar slants. —On beef agar and on potato agar a flat, bright yellow, especially 
greenish yellow, growth with somewhat irregular outlines is most frequent. Occa¬ 
sionally it becomes orange or yellow brownish (and the cells become in these cases 
fungoid). On mannite-nitrate agar the growth is thinner than on beef agar, often 
only dew-like and transparent. Phosphate agar gave a bright greenish yellow growth. 
The two red strains turned from whitish yellow to orange and later to brick red; 
their growth remained always very moderate. 
Beef gelatine gave only meager, thin surface growth, transparent or yellow; the 
gelatine remained either firm or showed after three to four weeks a little bowl-shaped 
depression, but only very little liquefaction. 
Beef broth became slightly turbid, contained some yellowish (or reddish) sedi¬ 
ment; but only in one case a loose, thin yellow film and a thin yellow ring were 
produced. 
Milk remained always unchanged, except in those cases where the cells assumed 
fungoid growth. Some yellow (or red) sediment was always noticeable; occasionally 
also on the surface a ring and a few flakes of the same color appeared. 
Potato gave growth, as a rule, only after repeated inoculation. Then a little 
transparent slime appeared, which changed with well-growing strains to a fairly thick 
greenish yellow (or brick red) slimy layer. Occasionally it became dull and dry 
(changing to fungoid type), or remained slimy, but turned brown (changing to large 
spore-free cells). 
