78 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[VOL. 11 



13. Isotachis obtusiloba Herzog, Beih. Bot. Centr. 60 (B) : 11. /. A. 1939. 



Isotachis mollissima Herzog, Revue Bryol. Lichenol. 23: 51. 10, a-d. 1954 



Plants of small to medium size, pale green, flaccid; stems slender, 3-5 cm 

 long, with leaves 2.5-3.5 mm wide, simple or irregularly branched; stems in 

 transverse section 16-18 cells in diameter, the unistratose cortical layer of small- 

 er, thick-walled cells. Rhizoids in tufts on the bases of the underleaves. Leaves 

 approximate, patent, broadly ovate-truncate to subquadrate, bifid to one-half of 

 their length or less ; segments broad, triangular, divergent, the sinus broad, V- 

 shaped; leaf margins entire or with one tooth midway or below on both sides; 

 cells of the median portion of the leaf averaging 73 X 33 jj., the walls thin, with- 

 out trigones, the cells of the margin and segments smaller, the cuticle smooth 

 to minutely striolate. Underleaves distant to approximate, broad, bifid to one- 

 half of their length, the margins with a large lateral tooth similar to a segment 

 on each side, rarely with additional smaller teeth. Male and female inflores- 

 cences and sporophyte not seen. Fig. 13, a-d. 



Habitat : In water. 



CHILE: Calbuco, Schwabe 155, (type Hb. Herzog); Pto. Magdalena I., Schwab e 20 

 b2, type of I. mollissima (Hb. Herzog). 



14. Isotachis lacustris Herzog, Hedwigia 74: 94. 1934. 



Plants of medium size, dark purple-brown, ascending to erect in tufts ; stems 

 stout, 4-5 cm long, the leaves 3-4 mm wide, occasionally branched; stems in 

 transverse section 14-16 cells across, the cortical cells in one or two layers, very 

 thick-walled, the cells of the medulla larger, with thinner walls. Rhizoids not 

 seen. Leaves widely spreading, canaliculate, broadly ovate to orbicular, bifid 

 to one-sixth of their length ; segments short, triangular, rounded at the apex, 

 the sinus V-shaped ; leaf margins entire ; cells of the median portion of the leaf 

 averaging 100 X 22 the walls thin, without trigones, cells of the segments 

 smaller, thick-walled, the lumina angular-rounded, the cuticle smooth. Under- 

 leaves only slightly smaller than the leaves, similar. Male and female inflores- 

 cences and sporophyte not seen. Fig. 14, a-d. 



Habitat : Growing in water. 



BOLIVIA: Illampu Peak, Mt. Sorata, Cordillera Real, C. Troll 56 (type Hb. Herzog). 



15. Isotachis obtusa Stephani, Spec. Hep. 6: 354. 1924. 



Plants of medium to large size, dark reddish-brown, ascending to erect; 

 stems 5-7 cm long, to 4 mm wide, occasionally branched; stems in transverse 

 section 16-18 cells across, the cortical cells in one or two layers, smaller than 

 those of the medulla, thin-walled. Rhizoids not seen. Leaves erect-spreading to 

 patent, very broadly ovate to orbicular, asymmetric, bifid to one-sixth of their 

 length or less ; segments short, blunt, triangular, divergent, the sinus V-shaped ; 

 margins of the leaves entire ; cells of the median portion of the lamina averag- 

 ing 84 X 40 p., the walls thin, without trigones, the cells of the segments sub- 

 quadrate, the cuticle smooth. Underleaves only slightly smaller than the leaves, 

 orbicular, bifid, the segments acute, connivent, the margins entire. Male and 

 female inflorescences and sporophyte not seen. Fig. 15, a-d. 



Habitat: In water. 



ECUADOR: Azuay: Paramo, Mt. Matanga, Allioni 6568 (type G). 



