1896.] The Bacterial Diseases of Plants. 641 
are destroyed at temperatures at which careless workers fre- 
quently pour their agar plates, while others refuse to grow at 
ordinary temperatures or even at blood heat, grow best at 50°-- 
60°C., and are not killed until the temperature exceeds 70° or 
even 75°C. Finally, a race of Bacterium anthracis incapable of 
producing spores has been developed by growing the organism 
in media containing phenol; another non-virulent race bear- 
ing swollen, terminal spores, “drumsticks,” by growing the 
organism in compressed air; and still another race destitute 
of virulence by cultivating it at temperatures above 40°C. 
These are not exceptional cases, similar care being necessary in 
all directions if one would avoid erroneous conclusions. 
Naturally, every successful experimenter will vary his culture 
media in all sorts of ways in order to learn as much as possible 
of the organism under consideration, but at the same time he 
will determine its behaviour on the standard media, and will 
keep a very careful record of all that he does. The bacterio- 
logist should make it an invariable rule to repeat every experi- 
ment two or three times, at the very least, and generally after 
an interval of some months or years he should repeat all his 
experiments. Even then he will fall into errors enough. He 
certainly should proceed with as much care as the chemist, 
and in many directions the work passes naturally over into 
chemistry. If quantitative or volumetric analysis requires 
all sorts of precautions and excess of care to avoid errors, no 
less does this youngest of all the sciences. 
A few words respecting the occurrence of bacteria in normal 
plant tissues will be in place before concluding these general 
remarks. It goes without saying that such minute and uni- 
versally distributed bodies as bacteria are likely to be found at 
times almost anywhere, even in plant tissues which seem to be 
healthy, just as they may sometimes occur in the blood stream 
of healthy animals, but they are not normally present in the 
tissues of plants. All carefully conducted experiments have 
led to this conclusion. The reader who wishes fuller informa- 
tion may consult papers by Laurent, Buchner,” Lehmann,” 
14b 
A ka redne greno bacterienne de la diastase. Buč. de l'Acad. 
15 (15) Notiz betreffend die Frage des Vorkommens von Bacterien in nor- 
eer? anzengewebe. Muench med, Wochenschrift., 1888, pp. 906-907, 
Erklarung in Betreff der Arbeit von Herrn Dr. Hugo Bernheim, ete. 
id, is , P. 110. 
