F, Section through the surface tissue of the Brown Alga Cutleria multifida, showing the surface layer of assimilating cells densely packed with phaeoplasts.
In Cutleria the laminated thallus is formed in the same way.
The asexual organs in the case of Cutleria multifida arise on a crustaceous form, Aglaozonia reptans, formerly considered to be a distinct species.
The four species - Ectocarpus siliculosus, Giffordia secunda, Cutleria multifida and Haplospora globosa - may be taken to represent, within the Phaeosporeae, successive steps in the advance from isogamy to oogamy.
Cutleria sp., margin of thallus showing trichothallic growth.
The spores of the Aglaozonia form are known to give rise to sexual plants, and the oospore of Cutleria has been observed to grow into rudimentary Aglaozonia.
To the specific identity of Haplospora globosa and Scaphospora speciosa, and of Cutleria multifida and A glaozonia reptans, reference has already been made.
Laminaria, Padina, Cutleria, Punctaria, Iridaea, Ulva, Porphyra, are leaf-like with a rigidity varying from a fleshy lamina to the thin and pliable.