,\l\'. 1907. p. 510, tab. XXX. 



mm. Linn. So Bol XIV. 1874. p. 151 tab. XI, fig. 1. 2. 

 imm Algues de la Guadcloupe 1870 77. p. 



in Journ. of Bot. XXVII. 1889. p. 70 pro parti 

 in Journ. ol Bot. XXVII. 1889. p. 238 pro parti 

 i Ie Toni Syll. Alg. 1. 1889. p. 513 (pro pari 



Green Alg. X. Amer. in rufts College Studie: II. [909. i>. 390. 



ui Herb. Mus. Brit! Rawsi Watts (Herb. Dickii ' 



,. Monti o Bay, /',./■< , Butler, Phyc. Bor. Amer. 771! Guadeloupe, Gosier, 



Herb. Mus. l>iit. and Herb. Kew ! Marie-Galante, M.i , n' [21 



Herb. Mus. lint. : Moule, Porte d'enfer, .1/./:. n° 175, r • sér. in Herb. Keu ' Bahamas, 



rry Islam . I rozen * a_y. Jan. $0. 11105, on rocks at low water mark, Howi n" 3572 (in 



Herb. Kew)! Bahamas, Mariguana, Abraham Bay, Howe in Phyc. Bor. Amer. n" 14S1! 



■ Mostly bright or sordid-green when living, becoming fuscous-brown or nigrescent on 

 drying, forming caespitose masses with usually crowded, sub-terete, fusiform, clavate, or finger- 

 shaped, sometimes capitate, often difForm, branched, and anastomosing lobes, never developing 

 .1 flabellum; lobes azonate mostly 4—12 cm. long and 0.5 — 4.0 cm. in diameter, now and 

 then disappearing in irregular cushions by fusing, the surface velutinous, spongiose, or sub- 

 strigose: filaments of the lobes subtorulose or the inner cylindrical with occasional constrictions, 

 always strongly constricted just above the dichotomy, rather thin-walled and somewhat easily 

 collapsible, 28 1. in diameter." M. A. Howe in Buil. Torr. Bot. Club XXXIV. 1907 p. 511. 



s- :"• 77]- 



We have availed ourselves of Dr. Howe's excellent description of this species. He has 

 had the opportunity <>f studying the plants in the living state and he says that they never 

 lop a truc flabellum. Among the flabellate species the nearest allies of . /. Rawsoni, as 

 structure and size of filaments, are A. Mazei anti A. nigricans. It differs from . /. Ma 

 in having its filaments mostly torulose and with thinner walls; and from A. nigricans in being 

 thin-walled, mostly pallid and merely torulose, never moniliform, and never markedly tapering 

 nor lly dichotomous at their apices. 



When examining the frond-filaments of . /. Rawsoni, we have often noticed the presence 



plugs (see fig. 771 in the constrictions above the dichotomies ; and since we 



. ed them in the vegetative frond-filaments of any other species, we are tempted to 



rd them as a character of specific value in . /. Rawsoni. Further their presence seems to 



■ : with the fact that the natural (original) apices of the filaments are generally 



We therefore infer either 1 t'n.it these stoppers serve to plug the filaments left 



bbled api es and so to arresl the escape of the protoplasm from the 



• that they are mere blockages whirh have herome acridentally lixed in 



. and have thereby caused the death and decay of the filament above. But 



n see no obvious reason why such a blockaee should cause the death of 



ient well provided with protoplasm and chromatophores, we are of opinion that 



the more probable explanation. Plugs of similar function i\xr found at 



