234 IMPORTANT VARIETIES OF FISSION-FUNGI. 



granular, gray (16, i). Surface growth : Irregularly round- 

 ish, with an almost even border, whitish-gray, with an 

 oily luster, soon extending to the wall of the tube. Later 

 it becomes yellowish-gray (16, n). 



Agar Streak. — Moderately spreading growth, wavy, 

 with a smooth edge, whitish-gray, shining, sometimes 

 appearing to be transparent in many places because of 

 porosity. The water of condensation is clear with slight 

 precipitate (16, v). 



Bouillon Culture. — Cloudy with abundant sediment 

 which is homogeneously distributed upon shaking. 



Milk Culture. — Milk is not coagulated even after stand- 

 ing for weeks. In spite of active multiplication, only very 

 little acid is formed. 



Potato Culture. — From the line of inoculation the 

 growth spreads quite widely as an extremely delicate, 

 moist, often almost entirely invisible layer (17, vn), 

 which, when touched with a platinum needle, may some- 

 times be drawn out into delicate slimy threads. This was 

 first described by Gaffky (Mitt. a. d. G. A. n, 372) as 

 characteristic, and was long held to be an important 

 specific characteristic, but it is not present in many cultures. 

 Other cultures, which grow typically upon acid potatoes, 

 present, at least upon alkaline varieties or alkalinized 

 portions, an atypical, luxuriant, grayish, white, or brown- 

 ish-yellow growth, which sometimes is moister, sometimes 

 drier, often not spreading much, and resembling the B. 

 coli. (Compare 18, ix. ) 



No Spore-formation.— The formations which were formerly held 

 to be spores, and which appear especially upon faintly acid potatoes, 

 are of two varieties, as first pointed out by H. Buchner (C. B. iv, 

 353). In unstained bacteria refractive polar bodies may be mistaken 

 for spores, but they stain especially easily with anilin dyes (quicker 

 than the bacteria) and do not impart any increased resistance to the 

 bacteria. In heated and stained preparations there occur vacuoles 

 which have a resemblance to spores because of their form and size, 

 and from not being stained by the ordinary methods, but such a 

 vacuole is never stained by the special stain for spores. According to 

 H. Buchner, these roundish vacuoles are located especially in the ends 

 of the rods ; according to Leo Miiller, especially in the middle, while 

 the stained masses occupy the poles. The Bact. coli shows much more 

 irregular and very inconstant vacuole formation. 



