REVIEWS AND CRITICISMS. 37 



to nine cells, each of which gives rise to an ascus, containing either 

 four 01' eight spores, according to the species. The asci soon become 

 free within the cavity of the peritheciura, which is formed by the 

 destruction of the other inside cells. The walls of the asci disap- 

 pear and the resulting spore mass is discharged through the neck of 

 the perithecium. 



The cell structure of the members of this group has much in com- 

 mon with that of the Floridese or Red Algse, and this resemblance 

 between the members of the two groups is heightened by the pos- 

 session by each of trichogynes and spermatia. The ascus represents 

 a structure which marks a wide morphological and phylogenetic 

 difference between the two groups, but the resemblances add a 

 strong argument to those being brought forward for considering the 

 Ascomycetes as derivatives from the same phylum with the Red 

 Algae. 



Professor Thaxter enumerates and describes 158 species, of which 

 only 14 were known previous to his own papers upon the group. 

 The genera have also been increased from 3 to 28. The hosts 

 number 250, of which 241 are beetles. Species are described from 

 all over the globe, but only a very few west American ones are 

 known to the author. — W. A. S. 



Analytic Keys to the Genera and Species of North American Mosses. 

 By Charles Reid Barnes. Revised and Extended by Fred 

 De Forest Heald. Madison, January, 1897. 



A LITTLE over ten years ago Professor Barnes published a set of 

 keys to the genera of mosses included in Lesquereux and James' 

 Manual. Four years later he published keys to the species of the 

 Manual, including also the new species described since the publica- 

 tion of that work. Both of these sets of keys proved very useful to 

 the students of mosses in this country, and the stock of available 

 copies was soon exhausted. In the present volume, prepared by 

 Professor Barnes and Mr. Heald, the keys have been revised and 

 brought up to date, and the descriptions of all species published as 

 North American, between the date of issue of the Manual (1884) 

 and January, 1896, have been added. 



Ninety-two pages are devoted to the keys and one hundred and 



