Fundamental Features of Phytocolloids. 13 



far before it became apparent that the temperature of the solution in 

 which the swellings were made was an indispensable feature of the 

 control, and as but few contemporary workers have recorded this con- 

 dition, it is not possible to cite their results with profit. 1 Some inter- 

 esting results are illustrated by the figures obtained without tempera- 

 ture control, which derive their value from the fact that all of those in 



FIG. 1. Auxograph arranged for recording changes in thickness of trio of sections of Opuntia and 

 of biocolloids. The vertical arm, which is set in position on horizontal arm to give an ampli- 

 fication of 20, rests on a triangle of glass laid on top of the sections. The dish containing 

 the sections rests on an iron cylinder to secure stability and a weight is placed on the T base 

 of the instrument. The record sheet is ruled to millimeters (not shown) with heavier hori- 

 zontal lines 1 cm. apart. The heavy curved lines represent hour intervals. The space is 

 ruled to 15-minute intervals (not shown). Height of clock and lever supports adjustable. 



1 MacDougal, D. T. The relation of growth and swelling of plants and biocolloids to tempera- 

 ture. Proc. Soc. Exper. Biol. and Med., 15 : 48. 1917. 



