1920 Pease; on Desmarestia 315 



Desmia ligulata Lyngbye Hyd. Dan. 3S. pi. 7 1819 



Postels and 



Ruprecht Illust. Alg. 13. 18iO 



Desmarestia ligulata I.amouroux Ess. 25. 1813 



Greville Alg. Brit. 37 pi. 5, 1830 



Kiitzing Phyc. Gen. 343. 1843 



Agardh, J.G. Sp. Gen. Ord. Alg. 1.2.1. 165. 1843 



Harvey Phyc. Brit. pi. 115. 1846 



Hauck ct Richtcr Phyc, Univ, 420. 1886 



DeToni Syl. Alg. 3:460. 1895 



Desmai-estia ligulata (Lightf.) Lamour. was first described by Light- 

 foot (1777) in the Flora Scotica as follows: "Fronde plana, avenia, sub- 

 triplicato-pinnata: ramis ramulisque distischis ; foliis lineari-lanceolatis. 

 spinoso-dentatis." Turner (1809) describes the type species as "frond car- 

 tilaginous, flat, almost nerveless, doubly pinnate ; segments linear-lan- 

 ceolate, serrated at their margins with spinous teeth." He also describes 

 two forms: "(3 angustior has its frond trebly pinnated, and nowhere above 

 two lines wide ; the teeth of its ramuli are so small and obsolete as to be 

 scarcely observable without a glass, whence the whole plant has a naked 

 appearance.' "Y dilatatus, which is a native of more southern seas, is dis- 

 tinguished from the specimens of our coasts by the width of its branches, 

 extending to four lines or more: its ramuli are nearly elliptical, and re- 

 markably attenuate at their base, so that they seem- to be supported upon 

 very short petioli." 



These three forms have not been kept separate, the difference in 

 growth habit being accounted for, no doubt, by difference in age or vigor 

 of individual specimens. 



Turner's descrij^tion, which is the most complete of those of the early 

 writers, calls attention to the irregular form of the holdfast; the almost 

 cylindrical base of the stipe; the narrow, flattened thallus, with branches 

 of various lengtlis, "the lowest generally longest, the uj^per ones regu- 

 larly shortest, but long and short mostly mixed together, all opposite and 

 undivided, but pinnated with others still smaller, arranged in the same 



manner, and these occasionally with a third series " These branches 



are "attenuated at their base and apices" and "separated by intervals of 

 two or three lines." This species was known to all the early Eurojiean 

 collectors, but was first collected on American shores on the coast of British 

 Columbia by Lyall, and identified b}' Harvey (1862). Harvey, however, 

 considered that this and the following species were identical, remarking 

 that "some of the sjjecimcns are of ordinary breadth; others are of the 

 widest variety constituting the D. herbacea of authors." Setchell and 

 Gardner (1903) quote Harvey, and remark that very few, if any, of the 



