PLATOMA-ARDREANUM (SCHIZYMENIACEAE, GIGARTINALES) AND HALYMENIA-CHIANGIANA (HALYMENIACEAE, HALYMENIALES), 2 NEW SPECIES OF PROLIFEROUS, FOLIOSE RED-ALGAE FROM THE HAWAIIAN-ISLANDS
Gt. Kraft et Ia. Abbott, PLATOMA-ARDREANUM (SCHIZYMENIACEAE, GIGARTINALES) AND HALYMENIA-CHIANGIANA (HALYMENIACEAE, HALYMENIALES), 2 NEW SPECIES OF PROLIFEROUS, FOLIOSE RED-ALGAE FROM THE HAWAIIAN-ISLANDS, Cryptogamie. Algologie, 18(2), 1997, pp. 97-116
Two superficially similar foliose algae with extensively ruffled surfa
ces are described as new species from the Hawaiian Islands. Platoma ar
dreanum Kraft et Abbott, sp. nov., is known from drift and shallow-sub
tidal reef flats and is the first central-Pacific member of its genus
to be reliably reported. Plants are characterized by: 1) lobed to dent
ate non-stipitate blades anchored by one to several crustose holdfasts
; 2) numerous ''calluses'' along lower blade margins; 3) conspicuous i
ntercalary ''gland'' cells; 4) monoecious gametophytes; spermatangia b
orne in patches on outer-cortical mother cells; 5) 3(-4)-celled carpog
onial branches, the basal cell of which often bears a 1- or 2-celled l
ateral; 6) supporting and epi-supporting cells that also bear 1- or 2-
celled laterals; 7) the longitudinal division of the presumably fertil
ized carpogonium, each half of which forms a stout fusion to an epi-su
pporting cell; 8) the growth of one or more connecting-filament organi
zing cells and the subsequent production of multiple branched, septate
connecting filaments from just one of the two contacted epi-supportin
g cells; 9) the septation of the connecting filament at its point of c
ontact to the lateral surface of the auxiliary cell and the ongrowth o
f the connecting filament to effect further diploidizations; and 10) n
on-ostiolate cystocarps. Features of the new species are compared to t
hose of the closest apparent relative, Platoma izunosimensis Segawa, f
rom southern Japan. Halymenia chiangiana Abbott et Kraft, sp. nov., kn
own from drift and rare attached collections, is characterized by: 1)
extensively ruffled and lobed blade surfaces and margins; 2) a filamen
tous medulla with stellate inner cortical cells and frequent refractiv
e ''ganglioid'' medullary cells; 3) occasional medullary filaments tha
t traverse the medulla to link the opposite inner cortexes; 4) more-or
-less flattened auxiliary-cell ampullae composed of sparingly branched
filaments that surround the base of an ostiole formed prior to diploi
dization of the intercalary auxiliary cell; 5) gonimoblasts developing
on auxiliary cells that fuse not at all or only slightly with adjoini
ng ampullar cells; and 6) tetrasporangia immersed in a modified cortex
of anticlinal filaments. Comparison is made to previously described H
alymenia species from the western Pacific.