90 
THE SEAWEEDS 
DICTYOTA Lamouroux. 
Frond flattened, ribless, dichotomous. Two strata of cells, the inner 
(medullary) of parallelepipedal large empty cells in a single layer, the 
external (cortical) of minute cubical or elongate cells, stuffed with dark- 
brown endochrome. All the reproductive cells derived from the cortex, 
oogonia in spot-like sori, of larger cells ; antheridia minute in sori of 
hyaline cells arranged perpendicularly to the surface; tetraspores scattered. 
Fig. 50. — (a-e) Dictyota ; (a) female sorus; (b) male sorus; (c) Sporangia 
and hairs; (d) tetraspore; (e) cross section of Dictyota ; 
(f) cross section of Pachydictyon; (g) cross section of Dilophus 
cruciately divided — all on different individuals. Colour olive-brown, 
becoming verdigris green when exposed to the air and sun or fresh water. 
There are 19 known Australian species. Of these the following are 
selected as occurring, or likely to occur, in South Australia. 
Dictyota latifolia J. Agardh. 
Frond about 30 cm. high, dark-brown coloured, inclined to blacken when 
dried, with filiform attachment, cuneate stipes and few dichotomous lobes 
2.5 to 5 cm. wide, at length covered on the surface by tongue-like 
prolifications. Spores scattered over the surface. 
Investigator Strait. 
Dictyota vittarioides J. Agardh. 
Like the preceding but with long narrow and rather simple divisions. 
Encounter Bay. 
