1896] BRIEFER ARTICLES 259 
Clinostat (#7. 7X ).—The phenomena of heliotropism and geotropism 
are of such fundamental importance that I believe it would not be out 
of place to offer demonstrations of them in secondary schools, espe- 
cially since our elementary text-books lay some stress on plant 
physiology. It was partially with this idea that this instrument was 
devised, and in its construction we have endeavored to obtain a cheap 
and compact piece of apparatus, and one at the same time which will 
illustrate all of the principles. Undoubtedly the best clinostat which 
has been devised for general purposes is that of Pfeffer, made by 
Albrecht of Tiibingen at a cost of $80. It can be adjusted to different 
rates of speed and is furnished with a powerful spring which enables it 
to run twenty-four hours without rewinding. An excellent clinostat is 
that of Wortmann, made at Strassburg, and costing about $60. So far 
as compactness is concerned this is the best, but a great drawback is 
that it has to be wound every twelve hours. Every laboratory where 
plant physiology is taught should endeavor to have one of the above, 
but when it is necessary to have more than one, or in case an instru- 
ment for illustrative purposes only is needed, a simpler and cheaper 
one will frequently answer as well. Such an instrument I have used in 
modified forms for three years. Briefly stated, it consists of an eight- 
day spring Waterbury clock (figs. s and 2) with a disk attached to the 
hour hand spindle which moves a shaft provided with a small friction 
— to which the plants are attached. The disk (c) is of aluminum 
2” thick and 47" in diameter, fastened to the hour hand spindle by 
pees OF & set screw. The hour. hand spindle is lengthened to 
extend be 
a be 
Thi 
the 
the 
co : the disk there is a steel rod shaft (/) which runs ona 
Vided oak « wa ane in an elongated bearing at the top and is pro- 
and at right Swivel joint to prevent lateral friction. On this ~— 
a. des the disk there is a small brass wheel (4) 2 in 
Outact with — with a solid rubber ring, a tire, which is in direct 
Fevolves whe : € disk. This wheel constitutes a friction wheel and 
nin contact with the aluminum disk. It can be moved 
