162 



ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



KEY TO GENERA 

 1. Exceedingly gelatinous, irregularly alternately branched, small; 



sporangia zonate Dudresnaya 



1. Larger and firmer plants, bushy in habit; sporangia tetrapartite 



Leptocladia 



DUDRESNAYA Bonnemaison 1822 

 Dudresnaya colombiana n. sp.^^ 



Fragments to 5 cm long, at the thickest part to 6 mm diam., branching 

 1-3 times freely and irregularly, the branches tapering, to 1 mm diam. in 

 the upper divisions, which end in acute tips ; very softly gelatinous, easily 

 dissociated by pressure, pale rose pink in color; structurally showing in 

 the finer branchlets an axial filament 12-16 jn diam., at intervals of about 

 200 IX bearing contiguous whorls of determinate assimilatory branchlets ; 

 in somewhat older portions the axial filaments 20 ju, diam., surrounded by 

 numerous delicate longitudinal rhizoidal filaments, but near the basal 

 ends this axial filament obscure; assimilatoiy filaments slightly tapering 

 to their tips and the cells there shorter, oval, 4-7 /* diam.; carpogenic 

 branches present. 



Colombia: Valle, a few pieces from I. Gorgona, no. 34-495C (cysto- 

 carpic, TYPE), 12 Feb. 1934. 



LEPTOCLADIA J. Agardh, 1892 



Plants bushy, repeatedly alternately branched, the branches linear, 

 flat, with irregularly serrate margins and an obscure costa; in section 

 showing an axial cell row surrounded in turn by crowded slender fila- 

 ments, a pseudoparenchymatous zone and a cortex of anticlinal cell rows ; 

 tetrasporangia in sori, tetrapartite; cystocarps subseriate, immersed. 



KEY TO SPECIES 



1. Branching patent, the main axes vague above, 1-3 mm broad, the 

 branchlets irregular, flat L. Binghamiae 



1. Branching more erect, the main axes soon disappearing, 0.5-1.5 

 mm broad, the branchlets slender, subfiliform, compressed . L. laxa 



98 Dudresnaya colombiana n. sp. — Fragmenta molissima, ad 5 cm long., 6 mm 

 diam., irregulariter 1-3-ramosa, divisionibus superioribus 1 mm diam., cacummi- 

 bus aciitis; filamento axiali ad cacumina 12-16 n- diam., posterius 28 \i diam., 

 corticationem rhizoideam, ad basim invisibilem, habente; assimilatoribus ramosis 

 in axe verticillatis, subteretibus, cellulis externis ovatis, 4-7 \x diam. Planta typica 

 in loco dicto I. Gorgona, Valle, Colombia, legit W^. R. Taylor no. 34-495C, 12 

 Feb. 1934. 



