1917 • Pease; on Taxonomy of Desmarestia 389 



lamina. The midrib is slightl yprominent below, but gradually becoming 

 fainter upwards, with opposite veins which dissolve, even from the base, 

 into numerous fine veinlets." The description is accompanied by an ex- 

 cellent plate, and a discussion of the reproduction. 



While looking over a haul of material secured for the writer by means 

 of a trawl several young plants in various stages of development were 

 found (PI. 84, Figs. 2-6) which differ markedly from young plants of D. 

 herbacea brought up in the same haul. These plants are much broader, 

 round off abruptlj' at the base to a very short stipe, and are without lateral 

 branches; while in the young plants of D. herbacea (PI. 83, Figs. 1-4) 

 the thallus is comparatively narrow, tapers down very gradually to the 

 stipe, and lateral branches are well developed on very small specimens. 

 These new plants seem to correspond closely with Okamura's description, 

 and the writer feels safe in adding this interesting new species to the Des- 

 raarestias of the north Pacific coast of North America. 



After a careful study of material collected in the San Juan Islands, 

 from whose waters have been reported all the species of Desmarestia sup- 

 posed to occur on the north Pacific coast, and a comparison of this material 

 with descriptions, plates, and herbarium material of American and Euro- 

 pean collectors, the writer reaches the following conclusions: 



1. D. aculeata (L.) Lamour. is a fairly common species. It is easily 

 identified by its habit of adventitious branching and by the dark brown 

 color and hard texture of the older parts of the plant body. Only the 

 younger branches are discolored on exposure. 



2. D. media (C. A. Agardh.) Grev. is entitled to specific rank. It 

 is very abundant and can be distinguished from D. aculeata very easily by 

 its lighter color and softer texture, and by its behavior on exposure, the 

 whole plant body changing color, becoming flaccid, and rapidly decom- 

 posing. 



3. D. viridis (Muell.) Lamour. probably does not occur in this re- 

 gion. 



4. D. ligulala (iJghtf.) Lamour. is rare, but easily identified on 

 account of its narrow thallus, yellowish brown color, firm texture, and 

 comparatively small plant body. 



5. D. herbacea (Turn.) Lamour. is entitled to specific rank. It is a 

 very abundant species, at least in tlic Puget Sound region, and is unmis- 

 takable on account of its large size. It discolors quickly, and becomes 

 very flaccid and easily torn on exposure, and when dried becomes thin and 

 papery, and does not adhere to paper. 



6. D. tabacoides Okam. is a new species recently reported from the 

 Japanese coast, and is here reported from American shores for the first 



