Paraphenylenediamine, a new color test for lichens 



Raymond H. Torrey 



Dr. Alexander W. Evans, of the Osborn Botanical Labora- 

 tory at Yale University, has informed me of a new color test 

 for the genus Cladonia, which promises an interesting re-survey 

 of the reactions of its many species. He learned of it from Dr. 

 Heinrich Sandstede, of Germany, who reports that it was dis- 

 covered by a Japanese botanist, Asahina. The reagent is called 

 Paraphenylenediamine, or Paradiaminobenzine. 



Hitherto a solution of KOH, potassium hydroxide or caus- 

 tic potash, has been the reagent for determining the presence 

 of relatively large amounts of the bitter tasting fumarproto- 

 cetraric acid in lichens, and has been satisfactory in giving color 

 reactions in many species, which are helpful in separating them 

 from other species of somewhat similar appearance to the un- 

 aided eye or the hand lens. These reactions are described in 

 Lindau's "Die Flechten fur Anfanger," which a number of mem- 

 bers of the Torrey Botanical Club are now using for its excellent 

 plates; in Annie Lorain Smith's "Manual of British Lichens," 

 and in Dr. Evans "Report on the Cladoniae of Connecticut," 

 and I have followed these authorities in citing such reactions in 

 papers on the Cladoniae of our range and of the North Woods, 

 published in Torreya. 



But German botanists, especially Dr. Sandstede, have 

 named a number of species and forms on the basis of their taste 

 to the human tongue, whether bitter because of a relatively 

 large amount of fumarprotocetraric acid, or mild because with- 

 out it. Now, with the use of paraphenylenediamine, says Dr. 

 Evans, "it will no longer be necessary to taste our specimens." 

 His letter continues: 



"This is a crystalline substance, soluble in alcohol, and is 

 applied by means of a medicine dropper to the dry plant. If 

 fumarprotocetraric acid is present a yellow color quickly ap- 

 pears and the color deepens to an orange, orange red, or brick 

 red as the alcohol evaporates. If the bitter acid is not present, 

 the reaction is wholly negative or a pale and permanent yellow 

 stain results. Dr. Sandstede recommends that a small amount 

 of the reagent be dissolved in a watch-glass and tested in such 

 a very bitter species as C. coniocraea to see if the solution is 



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