70 



plasma with chromatophores and nuclei is contracted to an irre- 

 gular network or to more irregular clumps, from which the zoo- 

 spores are formed in good accordance with other algse e. g. Bry- 

 opsis, 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 ^'Egagro- 

 pi7a-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 annu- 

 lar constriction at the base of the branches ; further by the absence 

 of both the larger and smaller lentiform cells so characteristic 

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

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

 which are very regularly ramified with nearly all the branches 

 growing out from the top of the mother-cell (compare Kuckuck, 

 1. c, 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 similar 

 in several other regards, e. g. the formation of the zoosporangium ; 

 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 pro- 

 ducing 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 leave 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 Vaiil's Herbarium in the Botanical 

 Museum, Copenhagen, has first been described Ity KiiTziNG 



