In the Fucaceae, on the other hand, there is a single prismatic apical cell situated at the bottom of a groove at the growing apex of the thallus, which cuts off cells from its sides to add to the peripheral, and from its base to add to the central permanent cells.
In these brown types with bodies of considerable thickness (Laminariaceae and Fucaceae), there is, however, a further differentiation of the internal tissues.
This is the case in the Fucaceae, and in a very marked degree in the Laminariaceae in question, where the assimilative frond is borne at the end of an extremely long supporting and conducting stipe.
They consist of the following groups: - Fucaceae, Phaeosporeae, Dictyotaceae, Cryptomonadaceae, Peridiniaceae and Diatomaceae.
Fucaceae and Phaeosporeae are doubtless closely allied, and to these Dictyotaceae may be joined, though the relationship is less close.