156 es 
Gelatine was inoculated while liquid, then allowed to solidify. At the 
end of two days colonies appeared as small white dots beneath the sur- 
face of the gelatine. In gelatine thus inoculated with M. amylovorus such 
colonies were not apparent. 
Upon agar the only essential difference in the two germs that might 
be noted is that germ No. 2 grows much more rapidly than M. amylovorus 
does when exposed to the same temperature. 
This paper has been prepared under the direction of Dr. J. C. Arthur, 
to whom I am very much indebted for a number of suggestions which 
have been of great value in my experiments. 
WATER PoweER FOR BoTANICAL APPARATUS. By J. C. ARTHUR. 
In vegetable physiology a number of kinds of apparatus are required 
which must be run at an approximately uniform speed. Some of the most 
important of these pieces are used to influence the direction of growth, and 
as plant movements dependent upon growth are slow, the apparatus 
must often be kept in motion continuously from twenty-four to seventy- 
rwo hours or more. 
The chief reliance where the movement is very moderate, ranging as 
it does for clinostats between ten to sixty minutes for one revolution, has 
usually been some form of clock-work, regulated by escapement or fan. 
For comparatively rapid movement, such as a centrifuge requires, which 
ranges from fifty to five hundred revolutions per minute, recourse is gen- 
erally had to water or electric power. Both of these sources prove very 
unsatisfactory as a rule, for machines doing such light work as the physi- 
ologist requires, and especially when they must be run steadily and with- 
out interruption both day and night. 
Electric power from a commercial plant usually varies greatly, and, 
moreover, is rarely continuous for the twenty-four hours. If the power 
is taken from a battery of some form of cells, the difficulty of maintain- 
ing a uniform current is almost as great, beside the annoyance of caring 
for the cells. The potash cells, especially those sold under the name of 
Edison-Lalande, have given the best satisfaction for this kind of work of 
any so far tried in the laboratory of Purdue University. But even these 
are treacherous, and quite uneven. ; 
