“4 
_-and plate cultures made with the following resullS_— : 
Se eee re 
434 The Botanical Gazette. [November, 
Experiments on insolation. 
Although the fact that direct sunlight has a deleterious 
effect upon bacterial life in general has been known fora 
number of years!” the full significance of this has not been 
generally appreciated until very recently. Carefully conducted 
experiments have shown that many of the pathogenic forms 
are profoundly affected by direct insolation not only when 
they are in a vegetating but ina quiescent spore stage as well. 
The marine species isolated at Woods Holl have been tested 
in order to see whether forms naturally saprophytes were as 
easily affected as those accustomed to a parasitic mode of life. 
Bouillon cultures not more than twenty-four hours old were 
used as seed. From these control gelatin plates were made 
by using one loopful of diluted culture. Two parallel sets of 
bouillon tubes, each containing two or three cc. of fluid,were 
also prepared by using one loopful of culture as seed. One Z 
of these was then wrapped in several folds of black tissue 
paper, care being taken to insert small pellets of cotton bat- 
ting between the black paper and the glass of the tube, s0a5 
to diminish the effect of heat absorption and conductiog a 
culture liquid as far as possible. These parallel sets of cu 
tures were then exposed to the effect of direct sunlight ai 
the day. At the close of the experiment, the ee 
were filled with sterile gelatin and plate cultures ma ‘ 
that the total number of germs could be directly aie 
and compared with the control plate that showed the appr 
mate number originally seeded. 
Results of experiment were as follows: 
Series inoculated and exposed to direct sunlight. a1° C. 
April toth, 9 a. M. ky clear, temperature varied from 15- 
April 11th, sky cloudy all day. a 
April 12th, sky clear all day, temp. from 21-25° C. 22°C 
April 13th, sky clear (cloudy from I-3 P. M.), temp. i 3 
Series planted on April 14th. Bouillon in nen unwrapped 
tures appeared turbid with bacterial growth - spparently un- 
Gs ” : ctl clear an : i 
the ‘‘exposed” tubes were perfectly h sterile gelati® 
changed. These tubes were now filled wit 
NO. OF GERMS|| x9. oF GERMS IN sab 
NAME OF GERM. | ig sebieete | DARKENED CULTURE. ra 
ASS A | —Several thousand ‘ si 
| Several thousand o : 
Bacillus maritimus | 
15 
Bacillus litorosus 25 
Bacillus pelagicus 420 InnumerabX E 
12Downes & Blunt, Proc. Roy. Soc. 1877. 
