A. L. Smith, A Monograph of the British Lichens (2d ed.), Pts, I and II 

 (1918, 1926) ; Lindau, Die Flechten (1923) ; Zahlbruckner, Lichenes 

 (1926); Sandstede, Die Grattung Cladonia (1931); Zahlbruckner, Cata- 

 logue Lichenum Universalis, 9 vols. (1921-1932) ; Frey, Familie Umhili- 

 cariaceae (1933) ; Fink, Lichen Flora of the United States (1935). 



The Farlow Herbarium of Harvard University is very rich in lichens; 

 among its most important and valuable American lichen herbaria are 

 Tuckerman, Merrill, Riddle, Sprague, Taylor, and Robbins. Many Foster, 

 Grant, and Herre specimens are deposited at Farlow ; also Zahlbruckner 

 types and many exsiccati from all over the world. The Farlow Herbarium 

 has been used more than any other in the determination of specimens and 

 for the obtainment of distributional data. The University Herbarium at the 

 University of Michigan, where the large and important Fink Herbarium is 

 deposited, has been consulted freely. The study of specimens from the 

 Herbarium at the University of Washington has resulted in much interest- 

 ing distributional data. 



Much of the actual writing of this book has been done at Wellesley 

 College. The Herbarium of Wellesley College contains many lichen types 

 and valuable collections, and the library is unusually rich in lichen litera- 

 ture. For many years there has been a botanist at Wellesley especially inter- 

 ested in lichens. The first was Miss Clara E. Cummings, who was followed 

 by Dr. Lincoln W. Riddle and Miss Mabel A. Stone. At the present time 

 I am carrying on the tradition. We have all been responsible in some way 

 for the extensive lichen herbarium and library at Wellesley College. 



The value of color changes, brought about by certain chemical reactions, 

 has long been recognized for the determination of lichens. In this book color 

 reactions in combination with morphological characters have been used 

 for the determination of certain lichens. However, these color reactions 

 have not been used alone, as key characters. The chemicals used are para- 

 phenylenediamine, potassium hydroxide, and calcium hypochlorite. In most 

 tests, each reagent is applied separately, but in some potassium hydroxide 

 is applied first and this is followed by calcium hypochlorite. A positive color 

 reaction with one or more of these reagents indicates the presence of certain 

 lichen acids. Iodine solution is used as a test for the presence of various 

 carbohydrates. 



All specimens were collected by the author, unless otherwise indicated. 

 Most of the altitudes given, for specimens collected by me, were estimated 

 from topographical maps published by the United States Department of the 

 Interior, Geological Survey. No altitudes of less than 200 feet have been 

 reported. 



I have used the classification and nomenclature of Zahlbruckner, as given 

 in his catalogue (1921-1934), unless otherwise indicated. 



I wish to express my sincere appreciation of Dr. D. H. Linder (now 

 deceased), former Curator of the Farlow Reference Library and Herbarium 

 of Cryptogamic Botany of Harvard University, for the generous use of the 

 facilities of the library and herbarium ; and to Miss Hilda F. Harris, libra- 



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