365 



in the neighbourhood of the auxiliary branch, the conjugating tube 

 being by reason of this much shorter and thicker than usual. 



After the fusion with the conjugating tube the auxiliary cell 

 cuts off a small cell at its upper end, the central cell, and, after nume- 

 rous divisions this one gives rise, according to OSTERHOUT, to the 

 gonimoblastic filaments from which the carpospores are developed. 

 At the same time the pericarp is formed from the sterile cells. 



The ripe cystocarp is a nearly spherical body lying imbedded in 

 the cortical layer and extending far in to the medulla; it has a 

 well developed carpostome. 



An interesting fact is mentioned by OSTERHOUT. The tetrasporic 

 plant is often provided with numerous short proliferations protruding 

 to all sides. These originate from germinated tetrasporangia. 

 A whole tetrasporangium is required for each proliferation. 



The plant has been found with tetrasporangia, antheridia and 

 cystocarps in the months January to March. It is gathered in shal- 

 low water with the exception of a single specimen dredged in a depth 



of about 30 meters. 



The plant seems to be rather common at the islands. St. Croix: 

 Christianssteds Lagoon, Saltriver, near Lt. Princess. St. Thomas: In the 

 harbour of Charlotte Amalia. St. Jan: Cruz Bay, off America Hill. 



Geogr. Distrib.: Warmer part of the Atlantic coast of North 

 America, West Indies. 



Subfam. 2. Solierieae. 

 Rhabdonia Harv. 



1. Rhabdonia ramosissima (Harv.) J. Ag. 



J. AGARDH, Epicrisis, p. 593; Till Algernes Systematik, 4de afd. VII, 

 Florideae, p. 85. 



Chrysymenia ramosissima Harv. Nereis Bor.-Am., p. 190, pi. XXX B. 



f. dilatata J. Ag., 1. c., p. 85. 



The specimens found belong to the above form. The plant is 

 fastened by means of a small disc. The thallus is at first nearly 

 terete, but becomes soon compressed. The branches are given off 

 from the edges and mostly regularly opposite, now and then also 

 alternating or unilaterally. In vigorous plants this ramification is 

 repeated several times. The growing point is composed of nume- 

 rous diverging cell-filaments. Transverse and longitudinal secsions 



