82 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



sisting of a medulla of elongated cells mostly 16-18 ju, in diameter, up to 

 150 )u, long, and a cortex of about 3 layers of smaller and shorter cells, 

 the outermost angular, isodiametrical, about 5 ju, in diameter; secondary 

 pits conspicuous in the medulla; central axial filament often readily 

 observed in transections of young material, surrounded by 6-7 pericentral 

 cells; rhizoidal filaments absent; reproduction by spores unknown. 



Type: Holotype is Dawson 6808, Mar. 11, 1949, on sheet 54721, 

 including vial 2149 and slide 1301, in HAHF. 



Type locality: Intertidal rocky shore at Cabeza Ballena, Nov. 9, 

 1946. 



Additional material: D. 7083, Punta Frailes, Mar. 13, 1949. 



The conspicuous erect ligulate blades are at first suggestive of a 

 Gelidium species, but the total absence of rhizoidal filaments and the 

 creeping, penetrating, subcylindrical basal branches are indicative of 

 Gelidiella even in the absence of reproductive material. The peculiar 

 detachable character of the secondary branches, partly ligulate and partly 

 subcylindrical and in turn branched, seems to indicate a function in 

 vegetative reproduction. 



Gelidiella acerosa (Forsskal) Feldmann & Hamel 



Feldmann & Hamel, 1934, p. 533; Dawson, 1944, p. 261 ; Dawson, 

 1949, p. 246. Echinocaulon acerosum (Forssk.) B^rgesen, 1932, p. 5, 

 pi. 1, fig. 3. Fiicus acerosus Forsskal, 1775, p. 190. 



Thalli loosely matted or caespitose, with free parts to 5 cm. high, 

 consisting of numerous spreading, semi-erect or arching, non-percurrent, 

 semi-rigid, cartilaginous axes from a tangle of stolons growing in and 

 around sand and debris, and in part attached to rocks or crustose coral- 

 lines ; primary branches cylindrical to compressed, up to 1 mm. in dia- 

 meter, with 1-3 orders of branches, the first sparingly alternate, the ulti- 

 mate and subultimate alternate, subopposite or secund, closely spaced, of 

 more or less uniform length; branch-tips often curved downward and 

 becoming attached ; apex of branches with a distinct apical cell ; tran- 

 section showing a medulla of cells mostly 25-35 /x in diameter, grading 

 into a cortex of small pigmented cells 6-7 /* in diameter, the outermost 

 somewhat anticlinally elongated ; rhizoidal filaments absent ; central axial 

 filament sometimes distinguishable as a smaller cell surrounded by 5-6 

 cells of smaller diameter than the adjacent medullary cells; tetraspor- 

 angia borne in ultimate branchlets whose fertile ends are swollen to 

 about twice the diameter of the sterile base, cruciate ; sexual reproduction 

 unknown. 



