40 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 12 



A plant of shallow, protected situations, growing on rocks and wood- 

 work. 



Ecuador : Archipielago de Colon, among shore rocks, I. Fernandina, 

 no.i^-755. 14 Jan. 1934. 



MONOSTROMA Thuret, 1854 



Plants at first saccate, later usually splitting into broad, flattened 

 blades or narrow segments ; ordinarily of one cell in thickness ; cells with 

 one or two platelike chromatophores, each with a pyrenoid. 



KEY TO SPECIES 



1. Plants without differentiated stalklike portions, broadly foli- 

 aceous, only incidentally cleft M. ecuadoreanum 



1. Plants with narrow stalklike bases, definitely lobed above . . 

 M. dactyliferum 



Monostroma ecuadoreanum n. sp.*<> 



Plants gregarious, broadly foliaceous or sparingly cleft ; green, becom- 

 ing brown on drying, 1-3 cm tall, the thallus of one cell layer, the cells in 

 surface view closely placed, angular, 10-24 fi (averaging 18 /x) diam., with 

 the lateral walls 0.8 fi, the outer walls 1.5 /u. thick; thallus thickness 18-26 

 fi, the cells quite rectangular in section; chromatophores probably single 

 in each cell. 



In the genus Monostroma, the northern and much larger M. fuscum 

 and its varieties turn brown on drying and have two chromatophores in 

 each cell. These plants likewise turn brown and are no thicker than some 

 forms of M. fuscum (Wittrock 1866, p. 53; Collins 1909, p. 213; Set- 

 chell & Gardner 1920, p. 243), They may prove to be only a variety of 

 that species, but the tropical habitat makes this seem unlikely. 



Ecuador: Guayas, on the rocky southeast side of Pta. Sta. Elena, 

 Salinas, no. 34-465 (TYPE), 8 Feb. 1934. 



40 Monostroma ecuadoreanum n. sp. — Plantae brunneae cum exsiccatae sunt, 

 gregariae, 1-3 cm. altitudine, cellulis 10-24 (x diam., confertis, membranis externis 

 1.5 \i crassitudine; thallo 18-26 \i crassitudine, cellulis in sectione rectangularibus. 

 Planta typica in loco dicto Pta. Sta. Elena, Guayas, Ecuador, legit W. R. Taylor, 

 no. 34-465, 8 Feb. 1934. 



