1899] APPLIANCES FOR PHYSIOLOGY 261 
the cylinder. The pen is made from a piece of small glass tub- 
ing sharply bent so that both ends press against the cylinder, 
one end being open and smoothed and the other drawn out to 
acapillary point bent to press 
at right angles against the 
cylinder? It is then partly 
filled with chronograph ink. 
The cylinder is covered with 
thin smooth paper put on moist 
with one edge gummed down 
so that when dry it is without 
Wrinkles, Enough weight is 
added to the pen to make the 
wheel turn as the plant grows, 
and as growth occurs the pen 
descends, tracing on the paper 
a spiral line. If now a vertical 
line be ruled on the cylinder, 
the length of the parts inter-f 
sected by the spiral line will 
sive the exact growth per 
hour, of course magnified. If 
half-hour intervals are needed 
another line is ruled 180° eoth 
e si andthe paper between 
Ge ° femoved on one side, 
aie edges may be brought 
bear Siving half-hour in- 
ak a poetics these 
the ag plete from P ' 
r preservation. There may not be room tor po 
and Clock under the w ‘ ee be put upon 
different level € wheel and either they must be Pp ae 
through a ee or else the thread from the plant must hod 
in the figure ae si digiteae other smooth arrangement as > 
: his instrument is liable to the same errors 46 
*The fi 
zu ; 
Sure shows an earlier and less efficient pen. 
Fic. 3.—A recording auxanometer. 
