Howe: PHYCOLOGICAL STUDIES 501 
C. ON THE AMERICAN SPECIES OF THE HALIMEDA TRIDENS 
GROUP : 
Even before writing “ Phycological studies —II,” * in which we 
described Halimeda favulosa as a new species and followed Mrs. 
Gepp (Ethel S. Barton) and also Harvey in considering Halimeda 
Monile (Ell. & Soland.) Lamour. a mere variety or form, we had 
seen both Halimeda tridens + (H. incrassata) and H. Monile grow- 
ing in close proximity to each other in Bermuda, in Porto Rico, 
and in the Bahamas, and remaining apparently distinct. But the 
segments in both of these were subject to so much variation in 
outward form, even in different parts of a single individual, that 
plants from other localities would sometimes appear to occupy an 
intermediate position, and great as were the manifest differences 
between the best representatives of these two types it seemed diffi- 
cult to draw any satisfactory line between them. When, however, 
in December, 1906, and January, 1907, we again saw, in several 
localities in Jamaica, Halimeda tridens and H. Monile growing 
either side by side or within a few feet of each other and always 
maintaining their distinctive characters perfectly, the conviction 
was forced upon us that a mistake had been made in considering 
=. | eee 
* Bull. Torrey Club 32 : 563-586. fl. 27-29. 1905. 
t+ One who has seen an extensive series of West Indian Halimedas, either growing 
or in an herbarium, can scarcely have any serious doubts, we believe, as to the intended 
application of Ellis & Solander’s names Coradlina tridens and Corallina incrassata or 
as to the impossibility of drawing any reliable line of specific separation between the 
two. This being granted, the next question involves a choice between the two names, 
Published in one work at the same time. Mrs. Gepp, in her monograph of ‘* The 
Genus Halimeda”’ (Siboga-Exped, LX) has adopted the specific name sncrassaza, 
Presumably because Ellis & Solander’s description of their Cora/lina incrassata was 
accompanied by the more numerous and more detailed figures. The Rochester and 
the Philadelphia codes of botanical nomenclature give preference in such cases to the 
name having ‘ precedence of position,’’ which would here call for the adoption of the 
Specific name ¢ridens, the name which, fortunately, in America, at least, has been the 
More generally employed. The recent Vienna Code (Art. 46) provides that ‘* when 
Wo or more groups of the same nature are united, the name of the oldest is retained. 
If the names are of the same date, the author chooses, and his choice cannot be modi- 
fied by subsequent authors.’ In the case in hand, technical priority in the matter of 
Publishing a choice between the two names appears to lie, by a narrow margin, so far 
aS we can discover, with Mr, F. S. Collins, whose choice of Ha/imeda tridens appeared 
i print in November, 1901 (Proc. Am. Acad. Arts and Sci. 37: 24 while Mrs. 
Pp’s monograph, in which the name Havimeda incrassata is preferred, bears the date 
of December Ig9oI. 
