218 ORDER I. PSEUDOMONADALES 



Genus IV. Ferribacterium, p. 221. 

 aa. Coccoid to rod-shaped cells in masses in a gelatinous capsule. Usually show 

 an irregular arrangement of cells. 



Genus V. Sideromonas , p. 222. 

 2. Cells with a thin capsule with a torus, 

 a. Torus completely surrounds the cells. 



Genus VI. Naumanniella, p. 223. 

 aa. Torus open at one pole giving the wall the appearance of a horseshoe. 

 Genus VII. Ochrobium, p. 225. 

 II. Non-encapsulated cells which form deposits of iron compounds in the cell wall, on 

 the surface of the cells or in the surrounding medium. 



A. Cells coccoid. 



Genus VIII. Siderococcus , p. 225. 



B. Cells rod-shaped. 



1. Found in neutral or alkaline waters. 



Genus IX. Siderobacter , p. 226. 



2. Found in acid mine wastes. 



Genus X. Ferrobacillus, p. 227. 



Genus I. Siderocapsa Molisch, 1909. 



(Ann. Jard. Bot. Buitenzorg, 2 S^r., Supp. 3, 1909, 29; also see Die Eisenbakterien, 

 Jena, 1910, 11.) 



Si.de.ro.cap'sa. Gr. noun siderus iron; L. noun capsa a box; M.L. fem.n. Siderocapsa 

 iron box. 



One to many spherical to ellipsoidal, small cells embedded without definite arrangement 

 in a primary capsule. The primary capsules may be surrounded by a large secondary cap- 

 sule, and these may then be united into larger colonies. Iron compounds are predominantly 

 stored on the surface of the primary capsule, and when a secondary capsule is present, it 

 is also completely covered. 



The type species is Siderocapsa treubii Molisch. 



Key to the species of genus Siderocapsa. 



I. Several cells in each capsule. 



A. Attached forms. 



1. Cells small; up to 8 in number in each capsule. 



1. Siderocapsa treubii, 



2. Cells larger; up to 100 and more in each capsule. 



2. Siderocapsa major. 



B. Plankton forms. 



1. Primary capsules 3.5 to 9 microns in diameter, each containing 2 to 8 cells. 



3. Siderocapsa coronata. 



2. Primary capsules 10 to 20 microns in diameter, each containing up to 60 or more 

 cells. 



4. Siderocapsa eusphaera. 

 II. Only one cell in each capsule. Cells always small. 



A. Capsules attached. 



5. Siderocapsa monoeca. 



B. Capsules form unattached iron floes. 



6. Siderocapsa botryoides. 



