F. Børgesen: List of species. 469 



131. Digeiiea simplex (Wulf.) Ag. 



In a collection consisting of various algæ I have come across 

 the male plant of this species. The antheridial stands have pre- 

 viously been known only from a figure in Kützing's "Tabulæ 

 Phycologicæ", vol. 15, pi. 28, fig. m. Concerning this figure Fal- 

 kenberg in his monograph of the Rhodomelaceæ writes p. 160: 

 "Die Antheridien habe ich zwar nicht selbst gesehen, aber die 

 Abbildung Kützing's lässt wohl kaum eine 

 andere Deutung zu, als dass es sich bei 

 Digenia in der That um flache, ovale Anthe- 

 ridien handelt, die am oberen Ende der 

 Sprosse gehäuft stehen. Ich wäre eher 

 geneigt, die Abbildung auf misverstandene 

 eingekrümmte Blätter zu deuten, wenn ich 

 nicht bei Bryothamnion analoge flache Anthe- 

 ridien gefunden hätte". 



The male plants recently discovered by ^^ ^^■J.\%:'iZ- 

 me prove that Kützing has had such a mit of the thallus with 

 plant at his disposal. The antheridial stands '"'^About^'siv n"^ '" 

 are, when fully developed, discoid bodies 



of obhque reniform shape; their entire surface is covered by the 

 antheridia. 



A whole trichoblast is used to the formation of the antheri- 

 dial stand just as in the case of Bryothamnion according to Fal- 

 kenberg's description (1. c, p. 175), and its development takes 

 place in a very similar way. From an apical cell with two sides seg- 

 ments are cut off alternately at both sides. These segments or 

 branches remain together, increasing gradually in length and 

 at the same time dividing into smaller cells; and this process is 

 carried on until the above mentioned flat bodies are formed. 



The antheridial plant was found in the month of January 

 in shallow water near the shore. 



St. Croix: Lt. Princess. 



132. Bryothamnion triquetrum (Gmel.) Howe. 



133. — Seaforthii (Turn.) Kiitz. 



134. Herposiphonia secunda (Ag.) Falkenb. 



As pointed out in my previous description of Herposiphonia. 

 I was most inclined to consider the two species H. tenella and 



