X PREFACE. 



Partie Botanique,' containing the Ferns. On examining 

 it, to see if there were any individuals of the genus in 

 question, he found three ; viz., Cystopleris retusa, Decne., 

 C. dimidiata, Decne., and C. squamata, Decne. The first 

 two were, happily, accompanied with figures, from which, 

 no less than from the excellent description, it was quite 

 clear that C retusa was identical with C. fragilis (an uni- 

 versally diffused species) ; while C. dimidiata is the Da- 

 valUa (Leucostegia) immersa of this volume (p. 157), The 

 C. squamatUy of which there is no delineation, and only a 

 brief distinguishing character, it was not in his power to 

 identify, and it is accordingly here placed among the Spe- 

 cies dubite, in the Addenda. Even its genus must remain 

 doubtful ; it may be (and standing next after C. dimidiata 

 it probably is) a Davallia (Leucostegia, Pres/), rather than 

 a Cystopteris. 



The appearance of the ' Hymenophyllaceae ' of Dr. Presl 

 in England, exactly at the close of the printing of that 

 group of Ferns in this work, has given rise to some re- 

 marks upon that publication at p. 144, which will show 

 how widely at variance are the views, here propounded, 

 respecting Genera and Species, with those held by that 

 learned and indefatigable botanist. But scarcely had these 

 two veiy dissimilar arrangements of the tribe in question 

 come into circulation, than another appeared, from the 

 pen of the excellent Dr. Klotzsch of Berlin ; viz., * The 



