284 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



haps more than a decimeter; they are often abundantly perforate and the 

 holes, like the margin, fimbriate with small proliferations. The areas with 

 tetrasporangial sori are commonly darker than the sterile border, but the 

 extreme margin is sometimes notably dark red. 



Ecuador: Archipielago de Colon, a fragment dredged in 27-36 

 meters near Tagus Cove, I. Isabela, no. 34-1 38 A (tetrasporic), 13 Jan. 

 1934. Ibid., dredged ofiF Academy Bay, I. Santa Cruz, no. 34-307 (tet- 

 rasporic, TYPE), 20 Jan. 1934. Ibid., fragments dredged from 55 

 meters' depth off Black Beach Anchorage, I. Santa Maria, nos. 34-372, 

 34-390 (tetrasporic), 29, 30 Jan. 1934. 



AGROSORIUM Zanardini, 1869 



Thallus flat, freely branching in a plane from the margin, with micro- 

 scopic veins; growth not from a single apical cell; tetrasporangial sori 

 relatively large, single near the tips of the branches ; cystocarps scattered, 

 the gonimoblasts developing terminal carpospores. 



KEY TO SPECIES 



1. Definitely pointed or hooked branches present . . A. uncinatum 



1 . Pointed or hooked branches absent 2 



2. Segments between the branches 4-10 mm wide, little narrower 



in the upper than in the lower parts of the plant. . A. Papenfussii 

 2. Segments between branches 2-5 mm wide, considerably narrower 

 in the upper than in the lower segments A. fragile 



Acrosorium Papenfussii n. sp.^^^' ^^^ 

 Plate 95, Fig. 1 



Plants to 25 cm tall, delicately membranous in texture and dull rose 

 colored ; branching irregularly alternate to subdichotomous, occasionally 

 digitate, the segments 1-4 cm long, 4-10 mm broad, little narrower in the 

 upper than in the lower segments, strap shaped or a little broader at the 

 top of a segment, the margins entire to a little irregular, but hardly 

 crenate; branching somewhat erect, the angles generally rather narrow, 



180 Acrosorium Papenfussii n. sp. — Plantae ad 25 cm altitudine, delicatae, 

 ramificatione irregulariter alterna ad subdichotomam aut digitatam, segmentis 1-4 

 cm long., 4-10 mm lat., ligulatis, marginibus paulum irregularibus; furcatis in 

 angulis suberectis, sinibus rotundatis, cacuminibus obtusis; media in parte ad 6-10 

 cellularum crassitudinem crescentibus; venulis microscopicis, obscuris, anastomo- 

 sentibusque; cystocarpis marginalibus aut submarginalibus, prominentibus. Planta 

 typica in loco dicto I. Santa Cruz, Ecuador, legit W. R. Taylor no. 34-318B, 20 

 Jan. 1934. 



181 Named in appreciation of the studies on marine algae by Dr. George F. 

 Papenfuss. 



