The genus Bornetia (Rhodophyta, Ceramiaceae) and its Southern Australian representatives, with dscription of Involucrana gen. Nov

Abstract

Two species of southern Australian marine algae have been previously placed in Bornetia. One, B. binderiana (Sonder) Zanardini, shows the generic features of the type species from Europe (B. secundiflora), and an additional species, B. tenuis, is also described for the genus. Study of the type and the above two Australian species shows that Bornetia is characterized by subdichotomous filaments of elongate cells, a 5-6(-8)-celled fertile axis developing procarps successively and also non-functional pseudocarpogonia, an involucre produced from the lower cells of the fertile axis, and a large stellate fusion cell; and by the production of tetrasporangia and spermatangial heads in condensed clusters in which the terminal branch cells curve around the cluster as an involucre.

The other Australian species, B. ? Meredithiana J. Agardh, has procarps confined to the subterminal cell of a 3-celled fertile axis, and after fertilization sterile cells associated with the procarp produce an inner involucre around the carposporophyte, which has a massive fusion cell. Sessile polysporangia are borne in condensed lateral branch clusters. A new genus, Involucrana, is proposed for this species. Its relationships are probably with Sphondylothamnion, which also differs from other known Ceramiaceae in having a similar inner involucre.