METHODS USP;D IN THE STUDY OF STARCHES. 301 



chemical reagents are expressed in minutes. A different time column had to be given to 

 chromic acid (CA) because of its relatively much greater intensity of action, the abscissas 

 having witli this reagent five times the values of those of the other reagents. The abscissas 

 1 licrefore designate quantitative relationships, while each of the ordinates indicates a specific 

 reaction. Having the data, by marking upon the chart on the proper ordinates the several 

 \-alues of the reactions of the different reagents, and then drawing lines in regular order 

 from one mark to another, the curve of reaction-intensities was obtained. Rarely have 

 the reaction-curves been carried beyond the 60-minute line, because very few of the time- 

 reactions were observed bej^ond this period. In a mmiber of cases at the end of the section 

 on a family, as after Liliacea? and Amaryllidacea^, a group of curves is given which may be 

 taken tentatively as representing generic curves, that is, each shows the composite reaction- 

 curve of the starches of the genus, or the curve of a single representative of the genus. 



CHARTS OF COMPARATIVE REACTION-INTENSITIES OF STARCHES WITH EACH AGENT. 



Additional charts constructed on an entirely different plan from the foregoing will be 

 found in Chapter VII, pages 314 to 333. Each chart shows comparativehj the reaction- 

 intensities of all of the starches studied by means of a given agent; hence, there are sepa- 

 rate charts for polarization, iodine, gentian violet, safranin, temperature, chloral hydrate- 

 iodine, chromic acid, pyrogallic acid, ferric chloride and Purdy's solution reactions. These 

 charts have been plotted out on so simple a plan that no explanation is required in order 

 that they may be understood. 



NOTE IN REGARD TO PART II. 



As stated in the Introduction, in the final arrangement of this report it was foimd 

 necessary to cany the voluminous detailed accounts of the laboratory investigations, which 

 logically belong here, into a separate volume. 



