302 BOTANICAL GAZETTE [ocTOBER 
way to permit the disc to settle evenly upon the leaf surface no matter 
what the thickness of the leaf. 
Both instruments may be inked from an ordinary rubber-stamp pad, 
and the black record kind gives good results. Better, however, is a simple 
Fic. 1.—Space markers. x }. 
pad made from one fold of thin close cotton cloth attached by thread to an 
ordinary glass slide, and inked when needed by a mixture of three parts 
Higgins’ waterproof India ink and one part glycerin. 
XI, Demonstration auxograph 
Among the most important of the topics which all teachers desire to 
demonstrate in general botanical courses is growth, and this can be shown 
to complete satisfaction only through use of a recording instrument. Many 
recording auxanometers, or auxographs, have been described, but as yet n° 
practical instrument for educational purposes is obtainable by purchase. 
The essentials of a good demonstration instrument, aside from easy applica- 
bility to its work and durability, are reasonable accuracy, ready portability, 
visibility of record from some distance, and clear exhibition of its mechan- 
ism and principle. These ends, I believe, are well met in the instrument 
here described and illustrated (fig. 2). : 
It consists essentially of four parts: support-stand, recording cy linder, 
magnifying wheel, and plant-support. The support-stand is of rigid 
