PREFACE TO SECOND EDITION. 



The changes to the second edition are the addition of six 

 full-page half-tone illustrations of typical representatives of 

 the three gi'eat subdivisions of the lichens ; namely, the 

 crustose, foliose, and fruticose. These veill be of great 

 value to beginners in the study of this remai'kable group of 

 plants. 



Since the issue of the first edition no important discov- 

 eries have been made in lichenology, hence no changes have 

 become necessary in the text. 



I take this opportunity to express my obligations to Miss 

 Alice Eastwood, of the California Academy of Science, and 

 K. S. Gray, Attorney, San Francisco, for the loan of mate- 

 rial, as well as for assistance in collecting specimens. 



Albert Schneider. 



San rRANCisco, August, 1903. 



