1 66 BACTERIA IN RELATION TO PLANT DISEASES. 



able condition. The organism was a short rod, multiplying by cross-septation, 

 possibly also by means of spores, colorless, sluggishly motile, moving, it is said, by 

 means of one polar flagellum, and occurring abundantly in water containing rotten 

 vegetation, where bacteria would be likely to abound. It should also be noted that 

 it did not take up colored particles, such as indigo or carmine, when placed in water 

 containing these substances. If the word Bacterium is used, it should be in con- 

 formity to these facts, or supposed facts, and may be so used, I think, until they are 

 shown to be erroneous. 



The matter is simplified, however, if we start with Cohn's use of the word 

 Bacterium in the year 1872. The Bacterium of Cohn is a certain Bacterium 

 termo. While we are not able to tie down Cohn's use of this name to a particular 

 species, it appears that we can do it quite definitely to a group of morphologically 

 similar species. Much discredit has been thrown on Bacterium termo in modern 

 times, and it has been left out of many classifications. However, if one examines 

 into the matter, there is no reasonable doubt as to what Cohn had in mind. His 

 Bacterium termo was a small schizomycetous organism capable of growing freely 

 in Cohn's nutrient solution, containing acid potassium phosphate and ammonium 

 tartrate. It produced therein short rods (single, in pairs, or fours joined end to end) 

 and roundish-lobed (kugelige-traubige) white zoogloese, together with a greenish 

 I fluorescence. This is Cohn's statement and de Bary's. It did not 



appear in boiled fluids, i. <?., was destitute of endospores (Cohn), 

 and the motile rods were killed by a short exposure to 58 C. 

 (Schroeter). In other words, it was a non-sporiferous green- 

 fluorescent organism possessed of a single polar flagellum, or, in 

 some cases perhaps, provided with paired or triple polar flagella. 

 If we start with Cohn's classification in the year 1872, we may 

 p- | 37 * keep the name Bacterium for schizomycetous organisms of this 



type, and at the same time we shall not be doing any violence to 



the older use of the word by Ehrenberg, who figures and describes this kind of an 

 organism. This the writer proposes to do, substituting Bacterium (Cohn emend.) 

 for Pseudomonas Migula and for more recent names proposed by others. Cohn's 

 description, be it understood, is worthless for the most part, but his name Bacterium 

 (B. termo) is usable because it can be attached to a definite kind of organism. To show 

 that Cohn's use of this word and the writer's use of it do not conflict with former 

 usage, Ehrenberg's descriptions and figures of Bacterium are here reproduced from 

 the expensive and not readily accessible publications in which they appeared. 



The organism described as Bacterium triloculare by Ehrenberg is shown in 

 figs. 137 and 138, and Ehrenberg's account is summarized as follows: 



The genus Bacterium was founded by C. G. Ehrenberg in 1828, and was 

 characterized by him in the Symbolae Physicae, Animalia evertebrata. The book in 

 which this description occurs is an unpaged folio. On the second page of the text 

 proper, in a list of species found "In Oasi lovis Hammonis Siwae" this genus 



*FiG. 137. Bacterium triloculare. From Ehrenberg's Symbolae Physioe. Animalia evertebrata. 

 Decas prima. Berlin, 1828. Plate II, fig. 6. 



