Howe: PHYCOLOGICAL STUDIES 493 
from the medullary filaments, in most cases, at least, without any 
fusion, and often apparently lateral in origin (PL. 28, Fics. 1 and 
2). This latter condition is at variance with Mrs. Gepp’s conclu- 
sion (¢. c., p. 196) that in both the vegetative and reproductive 
parts of Halimeda “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 Halimeda 
tridens,* 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 PLATE 
27, FIG. I. In comparing it with the fertile specimens of 
#1, 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 7. 7una 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 
* kor remarks on the name of this species, see page 501. 
