s A Field Guide to the British Seaweeds - NMBAQC

Pilayella littoralis
Fine filamentous form with no distinct main axis, often confused with
other filamentous brown species such as Ectocarpus and Pilayella.
Profusely branched appearing hair-like, branches can sometimes be
secund and opposite but generally irregular. Characterised by its
discoid shaped chloroplasts and intercalary sporangia appearing as
swollen cells within the filaments throughout the plant. Found growing
within mixed mats on open hard or soft substrates and epiphytically
on Fucus or other large algae. Requires microscopic identification.
Growing on rock surfaces
and may also be found
growing along side
Enteromorpha on sandy
substrate
Intercalary sporangia
used to distinguish
from other brown
filamentous species