May 2,1921 
A Bacterial Budrot of Cannas 
149 
Gelatin stabs. —There is slight granular growth along the entire line 
of puncture, best at the top where it is sometimes villous or papillate, 
the length of the villi or papillae decreasing downward. Surface growth 
when 6 weeks old at 15 0 to 18 0 C. is thin, white, transparent, slightly 
rugose, with an undulate margin. No liquefaction occurs within two 
months at this temperature, but at 21 0 to 25 0 a saucer of liquefaction 1 
cm. deep may be formed within three weeks. Usually clusters of crystals 
form at the bottom of the liquefied part. 
Whey agar 1 plates. —Colonies on whey agar plates are white, round, 
convex, opalescent, with internal concentric markings by oblique light. 
On thickly sown plates by the third day, and on thinly sown plates by 
the fourth or fifth day, each colony is surrounded by a clear area 1 to 
2 mm. wide, beyond which a white halo extends outward (PI. 37, B). 
On thickly sown plates this involves the whole surface. As the colony 
grows it fills the clear space, even growing out into the white halo. The 
halo is composed of an alkaline precipitate, which is readily dissolved by 
acids. 
Whey agar slants. —Streaked from beef bouillon, growth is moder¬ 
ate, white, filiform, 2 to 4 mm. wide with undulate margins. The whole 
surface of the agar becomes white-clouded except for a clear area 1 to 
4 mm. wide closely surrounding the streak of growth (PI. 37, D). This 
halo is dissolved by acids. 
Potato cylinders. —Growth on steamed potato is scanty, spreading, 
dirty white, wet shining, transient, becoming pale brown. The potato is 
grayed. Diastasic action is feeble. 
Beef broth. Peptonized beef broth ( + 15) clouds weakly within 24 
hours at room temperatures (21 0 to 25 0 C.); often within this time it 
forms a heavier flocculent surface layer, which falls on the slightest agita¬ 
tion. In undisturbed cultures the clouding is often banded, the heavier 
bands at the top. A heavy, viscid pellicle forms, which often falls slowly, 
center first, the edges remaining attached to the walls, so that a hollow 
inverted cone is formed (PI. 37, A), which lengthens slowly to reach from 
pellicle to precipitate, and may persist for weeks. This occurs in both 
alkaline and acid bouillons. The abundant viscid precipitate is granular, 
semitransparent, and does not form a compact mass. It rises in a tena¬ 
ciously viscid swirl on shaking. Clouding becomes heavy and is per¬ 
sistent. 
Milk.— Milk begins to clear on the fifth to the tenth day, and clearing 
is complete within four weeks. No coagulation takes place. The milk 
becomes golden brown on long standing, sometimes with a jelly-like 
consistency. 
1 Formula for whey agar: To 3 pints of milk heated to boiling add a 20 percent solution of hydrochloric 
acid sufficient to coagulate the milk. Avoid excess of acid. Filter through cheesecloth. Add N/4.5 
sodium hydroxid until the whey titrates +7. To 500 cc. of whey add 150 cc. of water, 1.5 gm. of Nelson's 
photographic gelatin No. I, 7.5 gm. of peptone, 7.5 gm, of agar flour, and 7.5 gm. of saccharose. Dissolve 
by steaming 20 minutes, clarify with white of egg, tube, and autoclave 15 minutes at no® C. 
