BACTERIA 



IOQ 



resting stage may produce new threads of cells. Sometimes spores 

 germinate while still in the old thread (Fig. 88), giving a tangled 

 mass of cells or whorls of new threads at intervals on the old. The 

 conidia may be either motile or non-motile. The motility of these 

 conidia when it exists is due to flagella. 



Sheath. The threads of cells are sometimes surrounded by sheaths 

 of varying thickness. This sheath is a thickened and hardened mem- 



FIG. 88 Crenothrix polyspora Cohn, Brunnenfaden. (After Migula from Schmidt 



and Weiss.) 



brane, and forms a tube in which the different cells of the bacteria are 

 contained. This sheath is homologous to a capsule. In it are fre- 

 quently deposited characteristic by-products of the cell. In Creno- 

 thrix (an iron bacterium), for example, we have iron oxides. 



Among the iron bacteria are several interesting forms. Crenothrix 

 polyspora is one of the best known. Its general morphology is shown 

 in Fig. 88. The attached, sessile, threads are shown at a. The 

 tufts of short threads, radiating from the larger threads, are 



