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together and the coherence is moreover increased by means of 

 some small, short, rhizoids growing out here and there from the 

 filaments and attaching themselves very strongly to the neighbouring 

 filaments (fig. 17 h, i). 



Harvey gives in several respects a good description of the 

 development of the plant, but he lets firstly one cell be developed 

 at the top of the stem and this divides again successively once 

 or twice. 



As mentioned above, the head in the well-developed plant is 

 cup-shaped, being somewhat depressed in the middle, but one 

 also finds specimens with nearly ball-shaped heads as also others 

 more irregularly formed. In specimens growing in shallow water 

 the stipe reaches a length of about 4—5 cm and the head a dia- 

 meter of 3 cm , but in those from deep water the stem can even 

 be 15 cm long and the head 10 cm broad. In these specimens 

 the head was flattened and thin, forming a circular expansion, 

 most probably an adaptation to the subdued light. 



I may also add that old stems, having lost the head, are able 

 to produce a new; I have several times found very old stems 

 with a quite young, not yet annulated apex. 



As to the cell contents, we find in the wall-plasma the irre- 

 gularly polygonal plate-shaped chromatophores , forming by means 

 of their prolonged corners a rather dense network in the young 

 parts of the thallus (fig. 17 k), in the older the chromatophores are 

 of a more elongated form and more openly placed. In the middle 

 of the chromatophore a pyrenoid is present. Below the chromato- 

 phores the numerous nuclei occur distributed rather regularly. 



This species has been gathered in shallow water 2—3 feet, 

 and here in a rather exposed locality, and in deep water, down 

 to about 50 meters. 



It is found: St. Croix, at White Bay on the south side of 

 the island and St. Jan in the sea round this island: off Cruz 

 Bay, Marys Bluff, Ramshead, Annaberg etc. 



Botanisk Tidsskrift, 32. Bind. 



18 



