Howe: Pmvcological studies 511 



Avrainvillca nigricans Murr. & Hoodie, p.p. Jour. lk)t. 27 : 70. 



1889. Not A. nigricans Decaisne. 



Mostly brijj;ht- or sortiid-green when living, becoming fuscous- 

 brown or nigrescent on drying, forming cespitose masses with 

 usually crowded, subterete, fusiform, clavate, or finger-shaped, 

 sometimes capitate, often difform, branched, and anastomosing 

 lobes, never developing a 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 substrigosc : filaments of the lobes subtorulose or the inner 

 cylindrical with occasional constrictions, always .strongly con- 

 stricted just above the dichotomy, rather thin-walled and some- 

 what easily collapsible, 28-68 /i in diameter. [Plate 30.] 



Type locality : Barbados ; type in the herbarium of the 

 British Museum. 



Distribution : The West Indies. 



Apparently common in the West Indies, ranging at least from 

 the northern Bahamas to Jamaica and Porto Rico, growing from 

 low-water mark down to a depth of one meter, often on exposed 

 rocks near the low-water line. The species is represented in the 

 herbarium of the New York Botanical Garden at the present time 

 by specimens under seventeen collection numbers. No. jyo of the 

 Phycotheca Boreali-Americana of Collins, Holden, and Setchell, 

 issued as Avrainvillca longicaulis (Kiitz.) Murr. & Bood., and no. 

 yyi of the same series, issued as Avrainvillca nigricans Decaisne, 

 both collected at Montego Bay, Jamaica, by Mrs. C. E. Pease and 

 Miss E. Butler, belong with the present species, at least in the 

 three sets examined, though in one set, the material issued under 

 no. 770 is mixed with A. nigricans ; however, all three of the 

 species named are found at Montego Bay. Avrainvillca Kaivsoni 

 is the plant that we once* referred to as "what we believe to be 

 a low-littoral or shallow-water condition of Avrainvillca Mazci" 

 but since we have seen it growing profusely in deeper water in 

 Jamaica closely associated with both A. longicaulis {A. Mazci) and 

 A. nigricans and without showing the least tendency to intergrade 

 with either, we cannot do otherwise than consider it abundantly 

 entitled to specific rank. The plant evidently never develops a 

 true flabellum and the filaments are thinner-walled, more collapsi- 



* Bull. Torrey Club 32 : 568. I905. 



