Fig. 155. Fucus vesiculosus.

a. Upper part of a frond, with air vessels and receptacles.
b. Section of a receptacle.
c. Conceptacle.
d. Filaments and spores, of which the conceptacles are composed.
e. Filaments which issue from the pores on the surface of the frond.

This image is from Common Sea Wrack in Pereira's Elements of Materia Medica and Therapeutics, 1854.