322 Pub. Piiget Sound Biol. Sta. Vol. 2, No. 53 



In common with other ligulate species, a distinct midrib runs the length 

 of the main axis and gives off at regular intervals opposite branches which 

 extend to the edge of the frond and end in the spine-like teeth, or passing 

 through the attenuate bases of the lateral branches, become the midribs 

 of these structures, giving off in turn pairs of opposite branches which 

 extend to the margins. The midrib is much thickened in the basal portion 

 of the thallus. It also forms a ridge that can be felt with the finger in the 

 basal portion of the long branches. 



The one outstanding difference between this species and D. herhacea, 

 aside from the extreme difference in size, lies in the system of fine veins 

 which ramify through the laminae of the main axis and the lateral branches. 

 These veins do not originate from the midrib, but are given off as secondary 

 outgrowths from its pinnate, lateral branches. They are given off singly, 

 at irregular intervals, both above and below, branch repeatedl}', and form 

 a loose, irregular network in the lamina. The whole effect reminds one 

 strongly of the venation of a long narrow pinnately-veined leaf. Kiitzing 

 (1858) indicates this method of venation in his plate of D. herhacea f. 

 latior. 



Young plants ranging in length from 10 mm. to 50 cm. seem to show 

 that relative width of frond is determined from the beginning. Some are 

 relatively wide, with long wide branches, the branches equaling or exceed- 

 ing the main axis, while others are relatively narrow, with short, narrow 

 branches. These represent the extremes of the type however. In both 

 young and mature plants a fairly complete series has been secured, and 

 there seems to be no break in the progressive increase in width of the 

 thallus which would form a basis for dividing the species into two, or even 

 for segregating a form or variety. A factor which complicates the situa- 

 tion is that entire plants have not been found. Even in the smallest speci- 

 mens secured, the tipe of the long strap-like axis is worn away, so that the 

 real length of the j^lant in proportion to its width can not be ascertained. 



e. Desmarestia foliacea n. sp. 

 (Plate 58, Figs., 5-10; Plate 61, Figs. 1-5.) 



Fronde latissima, ligulata, simplici, tenui stijDitata, tenuissime mem- 

 branacea, margine irregulariter sinuata dentataque, dentibus distantibus, 

 costa media tenuissima et ramosa opposite percursa, ramis se ramulosis, 

 omnibus patentissimis, subtilissimis. 



Plant body comparatively small, up to 1 m. long; frond thin, mem- 

 branaceous, wide, strap-like, diameter to 15 cm.; unbranched; margins 

 irregularly sinuate with occasional obscure teeth ; midrib evident, with 



