REVIEW. 



JEpicHsis Systematis Floridearum. Auctore Jacobo Geokgio 

 Agardh. Lipsiae : apud T. O. Weigel, ISTG. 



After an interval of thirteen years Professor Agardh 

 has published, under the above title, the third volume of 

 ' Species, Geis^era, et Ordines Algarum.' The first 

 volume of the Avork, it will be remembered, contained the 

 Melanospermeee, the second, which was divided into three 

 parts, contained the Florideee. Of these parts, the first was 

 published in 1851, the second in 1852, and the third part, 

 which treated of the Rhodomele^ only, in 1863. 



Since the issue of the earlier parts immense numbers of 

 Algse, including a great many new to science, have been 

 brought from all parts of the world, and have been submitted 

 to scientific and accurate examination by algologists. The re- 

 sult of this examination has led to an acknowledgment that the 

 former system of classification, based upon the study of in- 

 sufficient materials, which were frequently misunderstood, 

 was defective, and that a new classification was necessary. 

 With this view the present volume has been prepared. 



As it is now understood that the determination of Algse 

 depends not so much upon outward form as upon micro- 

 scopical examination of the internal structure and fruit, no 

 apology is necessary for giving an account of Professor 

 Agardh's work in this Journal. 



The preface first claims attention, because in this the pro- 

 fessor refers to some points important to algologists. 



He notices first the mimicry of forms which is a frequent 

 feature in Algee as in other branches of natural history. Dr. 

 Harvey, in his beautiful work, the 'Phycologia Australasica,' 

 had before observed this, and had called attention to the re- 

 semblance in outward appearance between Delisea pulchra, 

 Vliacelocarpus LahillarcUeri, and Ptilota striata. The re- 

 semblance, how^ever, is only external, the internal structure 

 and the fructification being in each essentially different. 

 The instances cited by Professor Agardh are still more strik- 

 ing, because in them not only the outward form but the 



