186 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



7. Plants tufted, to 12 cm tall, much coarser with heavier segments 

 A. peruana 



8, Branches narrow, the segments not broad and foliaceous . 9 



8. Branches broader, since the segments become wide and subfoli- 

 aceous 1^ 



9. Plants very small, closely branched 10 



9. Plants of moderate size, of sprawling habit, the diameter of the 

 compressed branches to 2.0-3.0 mm, the segments often forking 

 very deeply once or even twice between successive articulations, 

 the segments sometimes truncate at the ends, sometimes with a 

 characteristic lunate incision, and the angles at the lower end 



even auriculate A. compressa 



9a. Habit more erect, segments 1.0-1.5 mm diam. . . v. tenuis 



10. Segments above strongly compressed, reaching 0.4-0.5 mm 

 diam,, or at most 0.7 mm at a fork A. Crosslandii 



10. Segments terete below, above very irregular, terete or flattened, 

 to 1.0-2.0 mm wide, or even to 3.0 mm below a fork; articula- 

 tions commonly absent at the forks A. polymorpha 



11. Large coarse plants, the segments bearing branches commonly 

 forked, the much-flattened upper branches reaching 2-4 mm in 

 width, most commonly more strongly convex on one side than 

 the other, upon which the conceptacles are borne, but not with 



a midrib A. dimorpha 



11. Smaller plants, the segments generally showing a distinct midrib 

 when flat and broad, though this may be indistinct when the 

 segments are narrow and linear A. foliacea 



Amphiroa minutisslma n. sp.^*^"^ 

 Plate 46, Fig. 1 



Plants 7-10 mm tall, tufted, closely dichotomously branched at angles 

 of 45°-60°, above somewhat complanate; segments terete below, terete 

 or very slightly compressed above, 250-350 (x diam. below, gradually 

 tapering, in the uppermost divisions about 200-250 fi diam., with truncate 

 tips, the flexible articulations very narrow, one cell in length, and the 

 calcified segments very short, 0.6-1.5 diameters in length; medulla with 



107 Amphiroa minutissima n. sp. — Planta ad 1 cm altitudine, arete dicho- 

 tome ramosa, segmentis calcifactis teretibus, ad nodum, autem, subcompressis, 

 infra 250-350 [i diam., supra 200-250 |li, 0.6-1.5 plo diam. longitudine; pericarpis 

 prominentissimis, 250-350 \i diam., in quoque segmento plerumque singulis, seri- 

 atim in ramo saepe contiguis. Planta typica in loco dicto Golfo Dulce, Costa Rica, 

 coll. W. R. Taylor no. 39-1160, 26 Mar. 1939. 



