2 Scientific Proceedings, Royal Dublin Society. 
mige Thallome von radiar gebautem Querschnitt und intercalarem 
Wachsthum. Vegetations- Faden aus mehreren oder, doch seltener, 
ans nur einer Langsreihe von Zellen gebildet. Pluriloculare 
Sporangien intercalar in den Thallus eingesprengt, nur aus einigen 
der ausseren oder auch aus simmtlichen Zellen eines Querschnitts 
gebildet ; bei einreihigen Individuen durch Theilung einzelner 
Gliederzellen in viele kleine Zellen entstanden.” 
Pogotrichum hibernicum oceurs on the thallus of Alaria esculenta, 
Grev., in the form of numerous small Edachista-like tufts of fila- 
ments, radiating from gall-like swellings (fig.1). The individual 
filaments of a tuft, not more than 1 cm. long, are seen, when 
examined microscopically, to vary much in thickness, some being 
only one cell thick, others many. All are provided with the usual 
pheeosporous hairs, scattered singly over their surface (fig. 3), 
and all or nearly all the filaments are, judging from my material, 
fertile, even when uniseriate. Hach filament has at its apex one, 
and, near its apex, usually several, of the just mentioned hairs. 
The growth of the filaments is intercalary, trichothallic, as, e. g., 
in Desmarestia. Each filament, when examined in cross section, 
shows itself to be radially constructed, solid or sub-solid, and with 
its axial cells the largest. Further, each filament is unbranched, 
as in P. filiforme, Reinke (fig. 3). 
Though the filaments of a tuft are unbranched, and, to 
this extent, unconnected with one another, they are, at their 
lower ends, in close contact with one another, and more or less 
fused into a compact body of a subparenchymatous nature. There 
are, too, to be observed, growing out from the superficial cells at 
the base of the filaments rhizoidal septate hyphee which come into 
contact with the surface of the A/aria thallus, and can, no doubt, 
give rise to new Pogotrichum filaments. On making a vertical 
section through the anchorage of Pogotrichum hibernicum it is seen 
to be not merely applied to the surface of the Alaria, i.e. epi- 
phytic, as a root-dise of a Fucus is to a stone, on which it grows. 
The individual filaments of P. hibernicum penetrate into the 
Alaria tnaiius, creep and ramify between both its cortical and 
medullary cells, the limiting layer of the A/aria being frequently 
obliterated during the process. Though I searched with =; mm. 
objective, I was not able to see a host-cell into the cavity of 
