F. Borgesen: Rhodophyceæ of the Danish W. Indies. 13 



and later by other investigators ^) that the freshwater Chantransiæ 

 were only stages in development of Batrachospermum etc. ^). 



NÄGELI published his genus Acrochætium in 1861. It was 

 based upon several marine forms known at that time. But in 

 those days the freshwater Chantransia were considered as inde- 

 pendent species, and these are, as is well known, so much like 

 the marine ones that Nägeli ought to have referred the marine 

 species to this genus as Thuret did some few years after. Had 

 Nägeli done so, we should not perhaps have been obliged to give 

 up this old generic name. 



Yet it should be born in mind that Schmitz 3) in 1889 

 reformed the genus Chantransia in a somewhat different sense 

 to Thuret namely without including the freshwater Chantransia 

 and in his sense therefore the genus equals Acrochætium. 



Owing to these facts it seems to me necessary to adopt 

 Nägeli's name. In connection with this I will transcribe Bat- 

 ters' conclusion as to this question. In his paper quoted above 

 he writes p. 58: "Under these circumstances it seems to me that 

 either the name Aiidouinella must be substituted for Chantransia 

 as that genus was understood by Thuret (i. e. to include both 

 freshwater forms, like C. chalybea and C. Hermanni, and marine, 

 like C. corymbijera, C. ejflorescens, and C. microscopica), or, as 

 seems preferable, to preserve the former name as that of a 

 -doubtful genus of freshwater algæ, and to adopt Nägeli's genus 

 Acrochætium for the reception of the well-understood marine forms". 



In 1904 BoRNET*) proposed to separate the species with 

 sexual reproduction from those bearing only sporangia the first 

 ones to be kept in the genus Chantransia the others to be refer- 

 red to the genus Acrochætium. I quite agree with Rosenvinge 

 that this distinction seems very artificial and in the following 

 survey of the species found in the Danish West Indies I follow 

 him and refer all the species to the same genus. 



1) Comp. De Toni, Sylloge Alg., vol. IV, Sectio IV, p. 1863, the note. 



^) Here I may call attention to the fact that Brand (in his paper: Über 

 die Siisswasserf ormen von Chantransia (D. C.) Schmitz, einschliesslich 

 Pseudochantransia Brand, "Hedwigia" vol. 49) has pointed out that 

 besides the Chantransia-like forms of Batrachospermum etc. there are 

 also some independent species of Chantransia and among these Ch. Her- 

 manni. This certainly needs further investigation. 



*) Schmitz, Fr., Systematische Übersicht der bisher bekannten Gattungen 

 der Florideen ("Flora", 1889). 



■*) BoRNET, E., Deux Chantransia corymbifera Thuret. Acrochætium et 

 Chantransia (Bull. Soc. bot. de France, T. 51, Paris 1904). 



