DIRECT READING PRECISION AUXOGRAPH 



The improved form of this instrument, originaUy designed and 

 perfected by Dr. D. T. MacDoiigal, has a compound lever by 

 which changes in length or thickness of plant organs may be 

 multiplied twenty to fifty times, and the variations traced con- 

 tinuously on paper ruled to 1 mm., making possible readings to 

 0.01 mm. 



The recording drum carries a seven-day chart (one day if desired), and is 

 driven by reliable clockwork. The records are not integrated but consist of 

 inked tracings on sheets of the same length as thermograph charts, so that 

 the course of growth and temperature may be connected directly. The drum 

 may be swung away from the pen lever and also adjusted vertically on its 

 support by a sliding sleeve. The lever system may be moved vertically by 

 a rack and pinidn to secure adjustment to varying lengths of a plant organ. 



This apparatus is designed for the stud}^ of the general course of growth, of 

 the influence of external conditions on the rate, the analysis of the "Stoss- 

 weise Anderungen" of Sachs, retractions, and changes of form in both limp 

 and rigid organs. 



A small number of tested instruments 

 now ready for delivery at $75.00 each 



THE PLANT WORLD, Tucson, Arizona 



