68 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 17 



congestis per regionem meduUarem, paucis in subcortice; cystocarpiis 

 solitariis, abundantibus, 350 ju, diametro, plus minusve terminalibus in 

 pinnis ultimis; tetrasporangiis in soris multo elongatis, ope marginum 

 distinctarum, sterilium terminatis. 



Thalli saxicolous, densely tufted, 3-4 cm. high, consisting of several 

 densely branched erect fronds from a small, discoid holdfast augmented 

 by a number of short, partially adherent stolons, sometimes the stolons 

 spreading a few mm. and giving rise to erect branches from secondary 

 attachment discs ; erect fronds stipitate, at first cylindrical but becoming 

 flat, 600-900 fx in diameter, 150-210 /a thick, consisting of 3 orders of 

 densely congested, pinnate, alternate or opposite branchlets, each order 

 successively narrow^er, ultimately to 300-200 ju, wide, closely spaced at 

 intervals of 1000-300 {x, progressively shorter toward the apex and form- 

 ing a rounded outline to the tuft, becoming deciduous in lower parts and 

 leaving the lower 1 cm. of the main axis bare except for short peg-like 

 remnants ; thallus in transection showing abundant longitudinal rhizoidal 

 filaments congested throughout the medullary region and only a few 

 scattered in the subcortical region ; cystocarps solitary, abundant, about 

 350 IX in diameter, more or less terminal on the ends of ultimate pinnae ; 

 antheridia unknown; tetrasporangia irregularly arranged in usually much 

 elongated sori often occupying the whole length of ultimate and sub- 

 ultimate ramuli, these ramuli expanded to 400-500 jx wide in fertile 

 areas and with a distinct sterile margin bounding the sorus. 



Type: Holotype is Dawson 4223, June 20, 1947, on sheet 54671, 

 including vial 2137, in HAHF. 



Type locality: On middle littoral rocks on the east side of the 

 North Island, Los Coronados, Baja California, Mexico. 



The densely tufted habit, the narrow, elongated tetrasporangial sori 

 and the medullary congestion of rhizoidal filaments mark this small 

 species as distinctive in the Mexican flora. 



Gelidium deciduum sp. nov. 

 Plate 5, fig. 4; Plate 22, fig. 1 



Thallis ad 20 cm. altis, multis frondibus erectis e haptero implicate 

 ramorum stolonoideorum ; caulibus primariis percurrentibus, infra 1.5- 

 2.3 mm. diametro, compressis, circa 1 mm. crassis, supra circa 1.5 mm. 

 latis, 350 fx crassis, parce ramatis, at in partibus superioribus multas pin- 

 natas ramulas spissas 3 ordinum parientibus, gradatim minores diametro 

 quam caulem primam, deciduas in partibus vetustioribus ; filamentis 

 rhizoideis parcis in medulla, congestis in zona peripherali circa 45 ix latis; 

 tetrasporangiis in soris ovatis in terminis expansis ramularum ultimarum. 



