Howe: PHYCOLOGICAL STUDIES 499 
exception longer than broad. The very different utricles of the 
subcortical layer, with other characters, well distinguish 7. cuneata 
from H. discoidea and we think it clearly entitled to specific rank. 
In any event, if one’s conception of specific limitations should 
prove sufficiently elastic to include the two under one specific 
name, Decaisne’s Halimeda discoidea has the right of way on 
priority grounds, 
The older writers on the species of Halimeda gave very little 
attention to histological characters. Kiitzing,* indeed, remarked 
upon the uniformity of their structure and considered it unneces- 
Sary to give detailed figures illustrating the anatomy of each 
species. Professor Askenasy + in 1888 made an important advance 
in describing and figuring the details of structure and ‘in empha- 
sizing their value in distinguishing species, but he apparently did 
not examine authentic material of certain species described by his 
ptedecessors, and thus quite naturally made a wrong application 
of some of the specific names. Mrs. Gepp (Miss Ethel Sarel 
Barton) in preparing her monograph of “The Genus Halimeda” 
(/ ¢.) recognized fully the importance of seeing original materials 
and rendered an important service by investigating carefully the 
characters of the nodal filaments of the central strand and insisting 
on the value of these characters in diagnosing species, but she did 
not emphasize sufficiently the characters of the peripheral utricles 
and the utricles of the subcortical layer, parts which, in most 
Species, at least, offer peculiarities of as much constancy and value 
as do the nodal filaments. That the nodal filaments are not 
altogether invariable is seen in Halimeda discoidea, where fusions 
of the H. Tuna type and of the 7. Opuntia type sometimes occur 
Side by side in a single node (FIGURES Ig and 20) and also in H. 
Monile, in which rarely the filaments are only superficially cohe- 
rent. The peripheral utricles and those of the subcortical layer 
also have, of course, a certain range of variation in each species ; 
nevertheless that range is limited and these elements possess char- 
acters of taxonomic value of which any final and complete system 
of classification must take cognizance. 
he specimens from Bermuda, Porto Rico, and Jamaica, which 
*Tab. Phyc. 7: 9. 57. 
t Forschungsreise $.M.S. Gazelle 4: 11-14. pl. 3, 4. 
° . 
