NO. 1 TAYLOR: PACIFIC MARINE ALGAE 107 



KEY TO SPECIES 



1. Thallus ligulate to foliaceous 2 



1. Thallus not foliaceous, but bushy with flat branches . D. tropica 



2. Plant freely branched, ligulate, narrow throughout, the margins 

 entire D. herbacea 



2. Plant larger, sparingly branched, the branches 2 cm broad or 

 wider, the margins with slender teeth D. munda 



Desmarestia tropica n, sp.'''® 

 Plates 18, 19 



Plants of moderate size, in excess of 4 dm tall, bushy, light brown, 

 soft; holdfast very small, little differentiated; stipe compressed, short, 

 about 3 mm broad, firm and fleshy, continuing as the rachis of the plant, 

 the first branches within 1-2 cm of the base; rachis to 5-8 mm broad, flat, 

 above hardly recognizable; main branches wide-angled, opposite, at inter- 

 vals of 1-3 cm, similar to the primary axis, and sometimes as large, re- 

 branching to more and more slender divisions in several degrees; midrib 

 represented by a faint line in the branches of intermediate age, but other- 

 wise generally not visible in surface view; branches of all degrees tapering 

 somewhat to base and apex, regularly beset with broad short teeth at 

 intei^vals of from 7-15 mm on the lower main axis, but of only 1-2 mm 

 on the lesser branches, these tipped with brown filaments in the youngest 

 parts, naked behind, and continued out to opposite spinose prolongations 

 or branches in the older parts ; brown filaments distichously closely oppo- 

 sitely branched, the primary filament a continuation of the tooth bearing 

 it, sharply tapered to the base, gradually to the apex, the cells 36-65 /x. 

 diam., almost moniliform, being strongly contracted at the septa. 



These plants represent a species of the greatest interest. They are rela- 

 tively coarse and fleshy below; above they become progressively more 

 slender and softer, but can scarcely be called membranous. They are 

 more bushily branched and with more gradation from base to apex than 

 in D. latifrons, and the branches are more expanded than in that section 

 of the genus. They are best included in the section Herbaceae, but are 

 clearly less membranous than the other North American representatives. 

 Among less well-known Desmarestias, D. anceps Mont. (Kiitzing 1859, 

 p. 41, pi. 98, figs, c, d) and D. distans (C. Ag.) J. Ag. (Kutzing 1859, p. 



7^6 Desmarestia tropica n. sp. — Planta altitudine maior 4 dm, fruticosa, succu- 

 lenta, stipite firma brevi compressaque, ramincatione opposita, stipite ad 5-8 mm 

 latitudine, supra vix agnoscibili; ramis patentibus versus basim apicemque paulu- 

 lum attenuatis, dentibus brevibus latisque, regulariter crebreque ornatis, qui, novi, 

 penicillis brunneis praefiguntur; costa obsoleta. Planta typica in loco dicto Post 

 Office Bay, I. Santa Maria, Ecuador, legit W. R. Taylor no. 34-388, 29 Jan. 1934. 



