10 Scientific Proceedings, Royal Dublin Society. 
Diagnosis of Pogotrichum hibernicum, sp. n.—Unbranched, 
tufted filamentous thalli, 1 em. long, of radially constructed cross- 
section, and intercalary growth. Basal cells of filaments rhizo- 
genous and penetrating <Alaria thallus to give new tufts by 
endophytic hyphe. Filaments hairy, each one assimilative and 
reproductive, solid or sub-solid. 
Chromatophores granular, 4-20, parietal. 
Sporangia unilocular and plurilocular in same tuft, but not in 
same filament, chiefly in upper parts of filaments, which part may 
become entirely converted into reproductive cells. Sporangia 
formed intercalarily, from individual joint-cells of thallus in 
uniseriate filaments, or from superficial cells, or from all the cells 
of multiseriate filaments. Fate of zoospores unknown. 
Habitat.—On Alaria esculenta, Grev. (young plants) at Kilkee, 
Co. Clare, in September. 
Affinities:—Very near to, if not identical with, Litosiphon 
Laminarie, Harv. 
Tur Laporatory, GLASNEVIN. 
EXPLANATION OF PLATE I. 
Fic. 1.—Tufts of P. hibernicum on Alaria esculenta, Grev., slightly mag- 
nified. The dark specks represent commencing tufts. 
Fie. 2.—A portion of specimen of fig. 1, seen edgewise. Slightly mag- 
nified. 
Fic. 3.—(a) Epiphytic part of a filament. x 60. 
(5) Cross-sections of various filaments. The more deeply shaded 
cells, s, represent unilocular sporangia, s’, emptied sporan- 
gium. x 240. 
(c) Basal region of epiphytic part of a filament, 7, rhizoids. x 240. 
Fie. 4.—a and b. Portions of two filaments showing unilocular sporangia. 
x 240. 
Fic. 5.—Upper portion of a filament with plurilocular sporangia (yp. s.); 
p'. 8’. dehisced plurilocular sporangia. x 240. 
Fie. 6.—Vertical section of Alaria thallus through Pogotrichum tufts. 
Slightly magnified. 
Fic. 7.—Vertical section of thallus of Punctaria, Grev., showing pluri- 
locular sporangia (p. s.) and hairs. x 240. 
