Howe: Phycological STUDit:s 493 



from the medullary filaments, in most cases, at least, without any 

 fusion, and often apparently lateral in origin (pl. 28, figs, i and 

 2). This latter condition is at variance with Mrs. Gepp's conclu- 

 sion (/. c, p. 196) that in both tlie vegetative and reproductive 

 parts of Ilalimcda "all fresh growth is preceded by a fusion of 

 filaments of the central strand," but in the specimen examined by 

 Mrs. Gepp the sporangiophores apparently arose only from the 

 segment-margin, in which case in the American plants also fusion 

 is the rule and perhaps universal. The sporangia of these Porto 

 Rican specimens vary from pyriform-obovoid to subglobose and 

 are 0.20-0.33 mm. broad ; in arrangement they are somewhat 

 botryoid or irregularly distichous. The plants were kept for a 

 time in a jar of sea-water with the hope that the living zoospores 

 might be seen, but the experiment was unsuccessful, probably on 

 account of lack of continuous observation. 



On March 22, 1906, the writer was so fortunate as to find near 

 Tallaboa on the southern shore of Porto Rico, growing in about 

 one meter of water (low tide), two fertile specimens of Halimcda 

 trideiis* a species which seems to have been known previously 

 only in a sterile condition, though it was originally described as 

 long ago as 1786 and has since been often collected. A photo- 

 graphic representation of one of these plants is given on platf. 

 27, FIG. I. In comparing it with the fertile specimens of 

 H. Tuna, one is impressed at first by the very different color 

 of the sporangia, which are uniformly yellowish-brown or of a 

 burnt-umber shade, while those of H. Tuna are uniformly of a 

 bright, dark, intense green. The sporangiophores are the most 

 densely clustered along the upper margins of the segments, espe- 

 cially at the apices of the lobes when lobes are present, but they 

 may emerge from any part of the segment and sometimes com- 

 pletely cover its surface. The second plant, the one not shown in 

 the photograph, is the more densely laden with sporangia, and 

 some of its branches are so thoroughly covered as to obscure their 

 segmentation. The sporangiophores are a little longer than those 

 of H. Tuna, ranging from 1.3 to 2.3 mm. in length, and they are 

 much more branched, being 1-5 times dichotomous. We have 

 not seen one wholly simple. The sporangiophores that spring 



* tor remarks on the name of this species, see page 501. 



