242 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



As a number of specimens and data have been contributed by others, 

 and as new material continues to come in, acknowledgement for these 

 will in most cases be postponed until completion of the systematic parts 

 of this series. 



A comprehensive key to the genera and species of Mexican Rhodo- 

 phyta will accompany the concluding part on this group in a later 

 volume. 



The descriptions of the species are for the most part drawn up from, 

 and intended to represent, the plants as they occur in the Mexican flora. 

 On this account, there may be instances in which the description does 

 not represent satisfactorily a variant of a given species from another part 

 of its range. 



Translation of the formal diagnoses into Latin was done by Dr. 

 Robert B. Cross. 



September 17, 1952 



