CONTENTS. 



rage 



Chap. I. On Collecting and Mounting Lichens, 7 



Chap. II. The Lichen, its Structure and Organs, 11 



Chap. III. The Distribution, &c., of North American Lichens, 21 



Chap. IV. The History of Lichens, 24 



Chap. V. Helps to the Study of Lichens, 28 



Chap. VI. The Arrangement of North American Lichens, 30 



Supplement, 45 



Plates — 1, Thallus ; 2, Gouidia ; 3, Apothecia, Spermogones 



and Pycnides ; 4, Spores ; 5-10, Spores of the Genera,. .60-72 



CORKECTION.— By a typographical error in the body of the work, Chap- 

 ters V and VI are numbered IV and V. 



