45 8 Johnson . — Two Irish Brown Algae : 
doch seltener, aus nur einer Langsreihe von Zellen gebildet. 
Pluriloculare Sporangien intercalar in den Thallus einge- 
sprengt, nur aus einigen der ausseren oder auch aus sammt- 
lichen Zellen eines Querschnitts gebildet ; bei einreihigen 
Individuen durch Theilung einzelner Gliederzellen in viele 
ldeine Zellen entstanden.’ 
P. filiforme , Rke., grows on the thallus of Laininaria 
saccharina and produces tufts 1-3 cm. long, the individual 
filaments being -oi 5 to -06 mm. thick and arising on a basal 
layer which is a single layer of cells, disc-like, and clinging 
to the surface of the Laminaria- thallus. The filaments are 
not provided with lateral hairs. The diagnosis I gave of 
P. hibernicum 1 is as follows: — ‘Unbranched, tufted, fila- 
mentous thalli, 1 cm. long, of radially constructed cross- 
section, and intercalary growth. Basal cells of filaments 
rhizogenous and penetrating Alaria- thallus to give new tufts 
by endophytic hyphae. Filaments hairy, each one assimi- 
lative and reproductive, solid or subsolid. Chromatophores 
granular, 4-20, parietal. 
‘ Sporangia unilocular and plurilocular in same tuft but not 
in same filament, chiefly in upper part 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.’ 
Thus while P. filiforme consists of tufts of delicate, naked 
filaments, provided with plurilocular sporangia only, and 
arising from an epiphytic basal disc, P. hibernicum , on the 
other hand, consists of tufts of thick coarse filaments, clothed 
throughout their length with hairs, and possessing unilocular 
or plurilocular sporangia. A basal disc is not present, the 
numerous filaments of a tuft are closely compacted together, 
rhizogenous and endophytic, the intracortical hyphae being 
stoloniferous. 
1 T. Johnson, Proc. Roy. Dublin Soc., n. s. I. 1, p. 10, PI. 1. 
