l62 BACTERIA IN RELATION TO PLANT DISEASES. 



Chlamydothrix Migula. 



Cells cylindric, non-motile, arranged in unbranched threads, with a sheath of 

 varying thickness. Frequently the septation of the threads is only demonstrable after 

 the use of reagents. Reproduction by means of non-motile, roundish or ovoid 

 conidia, which arise directly from the vegetative cells. Syn . : Streptothrix (Cohn) Mig. , 

 Leptothrix Kiitz. exp.', and Gallionella Ehrenberg exp. 

 Crenothrix Cohn. 



Cells united into unbranched filaments, attached, and gradually enlarging toward 

 the free end, i. e., with a distinction between base and apex. Sheath rather thick. 

 In iron waters the old and empty sheaths are permeated by ironoxidhydrate. Cells 

 cylindric or flat discoidal. Multiplication by non-motile (mostly roundish) conidia, 

 which arise from the vegetative cells by division and rounding off. For this purpose 

 the cells of the thicker threads divide in three directions of space, those of the thinner 

 threads only perpendicularly to the long axis of the thread. The conidia are discharged 

 and germinate immediately, often on the sheath of the mother-thread. Only one 

 species known. 

 Phragmidiothrix Engler. 



Cells cylindric, later discoidal, forming threads 100 ^ long and 3 to 12 ju thick, 

 with a very delicate, scarcely visible sheath. Multiplication by non-motile conidia, 

 which arise from the vegetative cell by division in three directions of space and 

 rounding off. Perhaps to be united with Crenothrix, if the projections observed by 

 Engler are not branches but epiphytes. Only one sort known. 

 Sphaerotilus Kutzing (1833). 



Cells cylindric, enveloped in sheaths, forming dichotomously branched threads 

 with no differentiation into base and apex. Multiplication by means of conidia, 

 which swarm out of the sheath, attach themselves anywhere, and immediately grow 

 out into new threads. The conidia possess a tuft of flagella inserted sidewise under 

 one pole.* 



Genera, the systematic position of which is doubtful : Spiromonas Perty ; Spiro- 

 discus Ehrenberg ; Achromatium Schewiakoff ; Newskia Famintzin ; Streblothrichia 

 Guignard. 



II. Order THIOBACTERIA. 



Cells without any "Centralkorper," but with sulphur inclusions. Colorless, or 

 pigmented rose, red, or violet by bacteriopurpurin ; never green. 



1. Family BEGGIATOACEAE. 



Filamentous bacteria, destitute of bacteriopurpurin. Division of cells in one 

 direction of space, viz, perpendicular to the long axis. 



Thiothrix Winogradsky. 



Threads attached, not uniformly thick, enveloped in a delicate sheath which is 

 not easily demonstrable, non-motile, contents containing sulphur granules. The 

 threads produce rod-shaped conidia at their end. These conidia, which are self-motile 

 by means of a slow, creeping motion, attach themselves by one end to any sort of 

 substratum, extrude a slime-cushion at the base, bend over ordinarily in their middle 

 to a nearly right angle and grow into a new thread. Habitat, hot sulphur springs. 

 Beggiatoa Trevisan. 



Threads destitute of a sheath, formed of flat discoidal cells, free, i. e., not attached. 

 Multiplication by folding and separation of the threads. Motile by means of an 



'Streptothrix and Cladothrix are omitted from the second volume, the species, so far as they repre- 

 sent bacteria, being distributed in other genera. C. dichotoma becomes SphcKrotilus dichotomus. 



