OF SOUTH AUSTRALIA. 
435 
develops into a lateral tuft of monosiphonous filaments; axes in some 
genera corticated by the development of a circle of pericentral cells, the 
first cell developing to the right of the displaced axis and the subsequent 
cells in a circle to the left from this, and also by the bases of the lateral 
filaments which may eventually develop into a heavy investment; lateral 
filaments in some cases becoming polysiphonous in the lower segments, but 
monosiphonous above and often ending in colourless filiform extensions, 
forking occurring by the formation of a new branch laterally from the sub- 
terminal cell ; sporangia produced in special polysiphonous swollen branch- 
lets or stichidia ; colourless spermatangia borne on lateral branchlets ; pro- • 
carps developed near the bases of the lateral tufts of filaments, the fertile 
pericentral cell producing two sterile initials and the four-celled carpo- 
genic branch, the auxiliary being cut off from the support near the carpo- 
gonium ; cystoearp enveloped by an ample ostiolate pericarp. 
The family Dasyaceae corresponds to the tribe Dasyeae of the Rhodo- 
melaceae in the old classification. 
Thuretia Decaisne, Dasya C. Agardh. Ileterosiphonia Montague. 
Haplodasya Falkenberg. Halodictyon Zanard. Tylocolax Schmitz. 
Family RHODOMELACEAE Oltmanns 1904. 
Plants usually bushy, sometimes sparingly branched; branches usually 
cylindrical, often delicate, occasionally flat ; growth from persisting apical 
cells producing an axial cell row ; branched colourless hairs (trichoblasts) 
often present, formed in a definite spiral sequence by segmentation from 
the upper margin of the primary axial segments before the formation of 
the pericentral cells ; axial cells generally surrounded at least in the fruit- 
ing portions by a series cut off from them by longitudinal walls (pericentral 
cells) producing a typically polysiphonous structure, the first developing 
directly under the initial which forms the trichoblast, subsequent peri- 
central cells originating to the right and left from this one, and the 
branches sometimes further corticated either by subsequent divisions of 
these to several degrees or by appressed rhizoidal down-growths ; sporangia 
formed on sporophytic (diploid) plants from internal segments of the 
pericentral cells, ultimately dividing in tetrahedral fashion, and the branch- 
lets bearing them usually little modified, but in extreme cases stichidium- 
like ; “antheridia” developed from trichoblast rudiments in the form of 
colourless tufts, cones, or plates of spermatangia; procarps developed from 
polysiphonous basal trichoblast segments, the last-formed and fertile peri- 
central cell as a supporting cell probably producing first the initial of a 
lateral group of sterile cells, then that of the four-celled carpogenic branch, 
and finally before fertilization the initial of a basal sterile group ; from the 
supporting cell beside the carpogonium after fertilization an auxiliary is 
cut off, from which, with a fusion cell organized after fertilization, the 
gonimoblasts are produced ; outer cells of the gonimoblasts alone forming 
carpospores ; cystocarps becoming enclosed by an ostiolate pericarp. 
