— 14 - 



This plant was collected twice: in the month of January (1896) 

 and in February (1892) in the lagoon at Christianssted, St. Croix, 

 and had at that time cystocarps and tetrasporangia. It was grow- 

 ing on the roots of mangrove in rather shallow and quiet water. 



Seirospora occideiitalis nov. spec, 



Fronde non corticata erectiuscula, alterne-decomposita-ramosa, 

 ramis ramulisque quoque versum egredientibus; articulis in inferiore 

 parte crassioribus, medio tenuioribus diametros quaternas vel quinas 



longis ultimis breviori- 

 bus et tenuioribus, saepe 

 piliferis. 



Tetrasporangiis ju- 

 venilibus ovoideis, adul- 

 tis fere sphseroideis, 

 sessilibus, triangule aut 

 rarius cruciatim di- 

 visis, 



Antheridiis eodem 

 modo ac tetrasporangiis 

 dispositis. 



Gystocarpiisgeminis, 

 in ramulis superioribus 

 natis, ramosis, ramulis 

 raoniliformibus , carpo- 

 sporis sphaericis in se- 

 ries dispositis. 



Fig. 8. Seirospora occidentalis nov. spec. 



A, base of a plant (25:1). B and C, branches with tetra- 

 spores (60:1). D, branch with antheridia (60:1). i*, anthe- 

 ridia (150:1). F, cells with chromatophore and nucleus (1.50:1) 



This interesting alga 

 I have found growing 

 among the above-men- 



tioned CalUtJiamnion 

 cordatum epiphytic on 

 Gracilaria Blodgettii, but not in great number. The plant reaches 

 a height of about 1 — 2 cm. The main stem, which is fastened 

 to the host plant by means of short thick-walled rhizoids emerging 

 from the lowermost cells, consists in the basal part of short, almost 

 as long as broad, thick- walled (the wall ca. AO/u thick) cells, about 

 200/^ thick or more (Fig. 8 ^4). Higher up the cells grow thinner^ 

 in the middle of the plant about 8b ju thick, becoming at the same 

 time more thin-walled and longer (4 — 5 times as long as broad), 

 decreasing in thickness evenly towards the apex, the ultimate cells 

 being only 8 — 11;/ thick. These often, but not always, end in a 

 thin hair (Fig. 8 Z>, 9.4). Breadth of the hair about 3^. 



