218 



The antheridial stands (Fig. 203 E, F) are found at the same 

 places as the tetrasporangia; they consist of a system of closely 



placed, short branches, of which 

 each bears 2 4 antheridia. 



The cystocarps (Figs. 202, 

 203 G, 204) are binate and trilo- 

 bed heart-shaped, sometimes also 

 more irregularly formed. The 

 younger and smaller ones consist 

 only of a single layer of carpo- 

 spores (Fig. 203 K), but in the 

 bigger cystocarps and especially 

 in the more irregularly shaped 

 several layers are also present. 



The carpogonial branch is 

 four-celled and possesses a very 

 long trichogyne (Fig. 203 /). 



Fig. 204. Callithamnion cordatum 



Borgs. Branch with cystocarps and 



a single tetrasporangium (50:1). 



The plant occurred as a com- 

 mon epiphyte on Gracilaria 

 Blodgetti and was found only 

 in deeper water (about 15 fat- 

 homs). It was collected with tetraspores, antheridia and cystocarps 

 in the month of March. 



Occurred in many places in the sound between St. Thomas and St. 

 Jan: off Cruz Bay. 



Geogr. Distrib. : Hitherto found only in the above mentioned locality. 



2. Callithamnion byssoides Arn. 



ARNOTT in HOOKER, English Flora, vol. II, part 1, 1833, p. 342 (Algae 

 by HARVEY). HARVEY, Manual, 1849, p. 178; Phycol. Brit. pi. 262. ARE- 

 SCHOUGH, I. E., Phyceae Scandin. Marinae, 1850, p. 107, pi. V, B. Cfr. 

 SCHMITZ, FR., in Berichte d. deutsch. bot. Ges., Bd. XI, 1893, p. 280. BORGE- 

 SEN, F., Some new or little known West Indian Florideae (Bot. Tidsskr.,' 

 vol. 30, 1909, p. 11). 



Regarding a comparison of the West Indian form with plants 

 from other countries I refer to my remarks, 1. c. Here I shall 

 restrict myself to give a short description only of the West In- 

 dian plant (Fig. 205). 



It has a rather vigorous main stem whose cells are about 

 3 4 times as long as broad (lat. cell. = 140//); higher up the 

 cells grow thinner and thinner, the youngest tips of the branches 

 being only 9 10 // thick. The branches emerge spirally from the 



