1917 Pease; on Taxonomy of Desmarestia 387 



DESMARESTiA viRiDis (Mucll.) Lamour., first published in the Flora 

 Danica (16), was reported from British waters by Stackhouse (29), al- 

 Iho it had been known to collectors for several years previously. It was 

 first reported from the Pacific coast by Postels and Ruprecht (21), and 

 according to Harvey (6) it was found at Esquimalt and Fuca Strait by 

 David Lyall. 



J. G. Agardh (2) distinguishes between the Atlantic and Pacific 

 forms, the latter being wider and evidently compressed. Saunders (25) 

 says that on the Alaskan coast it is not uncommon, but less abundant than 

 D. aculeata. He does not mention D. media, with which D. viridis is 

 •often confused. Setchell and Gardner (26) are in doubt as to the oc- 

 currence of the species in the region under discussion, because its resem- 

 blance to D. media and "lack of careful study of the 2 forms make it 

 uncertain at times to which species the references refer." 



Muenscher (18) says that "young specimens of this form {D. acu- 

 leata f. media) have been reported as D. viridis. A careful comparison 

 with both D. viridis and D. aculeata shows that they probably all belong to 

 the latter, at least none of them possess the characteristics of D. viridis." 



The writer has examined Miss Tilden's herbarium specimens No. 353 

 •of D. viridis collected at Minnesota Reef, San Juan Island, and Saunders' 

 No. 274 from Prince William Sound, and has compared them with herba- 

 rium specimens and preserved material in her own collection. All the 

 material examined seems to belong to the same species, and answers the 

 ■descriptions of various authors given for D. media. When compared 

 with specimens of D. viridis from the Atlantic coast, the difference is 

 plainly evident. Material collected by Holden (Phyc. Bor. Am. 11) on 

 Penfield Reef, Long Island Sound, is much more delicate than any Pacific 

 •coast material the writer has seen, having the truly capillary and exactly 

 ■opposite branching emphasized by European writers and so clearly shown 

 in herbarium specimens of Hauck and Richter's Phykotheka universalis 

 (No. 123) and Rabenhorst's Algen Europa's (No. 174^1). Moreover, it 

 is the consensus of opinion of European writers that D. viridis is an an- 

 Jiual, and it is so considered at the Marine Biological Laboratory at 

 Woods Hole. Specimens of Pacific coast plants collected for the writer 

 ^re undoubtedly perennial. Individuals over 100 cm. in length, collected 

 in April, have branches of the 5th and 6th orders, and show the hairs 

 of the transitory spring growth just beginning their development. 



So far as can be decided by examination of mature plants, the writer 

 is of the opinion that the occurrence of D. viridis on the Pacific coast 

 of North America is not yet established, and that the plants from this 

 region reported as D. viridis are in all probability /). medial. 



