— 263 — 



formed in good accordance with other algæ e. g. Bryopsis, Valonia 

 etc. As to the last mentioned genus Kuckuck in his paper 

 above-quoted has given a detailed description of the formation of 

 the zoospores based upon the study of living material. 



The plant occurs not only fixed but also loose as Ægagropila- 

 like clumps. These are very often cast ashore. In these loose- 

 lying specimens the basal part as described above is usually lacking, 

 and as most specimens collected are those cast ashore I think the 

 basal part will only seldom be found in the collections. 



As to the relationship of our plant I would point out that it 

 comes rather near to Valonia, Apjohnia, Siphonocladus etc. 



Though in several regards very like a Valonia I think that 

 our plant cannot in a natural way be placed in this genus. Thus 

 it differs from it by having a stem-like, annularly constricted, 

 basal part which is fastened to the substratum by means of irreg- 

 ularly ramified and septate rhizoids and by having a single 

 annular constriction at the base of the branches; further by the 

 absence of both the larger and smaller lentiform cells so charac- 

 teristic in Valonia. And to these characters we may add the very 

 regular ramification; to be sure we can find forms of Valonia 

 œgagropila which are very regularly ramified with nearly all the 

 branches growing out from the top of the mother-cell (compare 

 Kuckuck, I.e., p. 176, fig. 20) but some anomalies always occur. 



Compared with Siphonocladus tropicus, the basal part of both 

 plants seems to be quite alike and these plants are also very simi- 

 lar in several other regards , e. g. the formation of the zoosporan- 

 gium; but in the development of the thallus the difference on the 

 other hand is very great. 



And Apjohnia, which also comes near to our plant, differs 

 in several regards, in the annular constrictions not only of the 

 basal stem but also of the base of the branches and in the 

 very regular ramification, in the upper part of the thallus only 

 producing 3 branches. And these branches have no walls at their 

 base, only the above-mentioned constrictions which in any case in 

 the younger part of the thallus leaves a narrow passage open. 



This species, which has already been gathered at St. Croix by 

 West who called it Conferva diaphana and of which well-kept 

 specimens are still preserved in Va hl' s Herbarium in the Botanical 

 Museum, Copenhagen, has been described by Kützing upon spec- 

 imens also from this island. It is rather common here, occurring 



