508 HoweE: PHYCOLOGICAL STUDIES 
mented on the characters of the original specimens of Avratnvillea 
nigricans Decaisne and Riipilia longicaulis Kitz. Since that time 
we have enjoyed the opportunity of seeing again living plants of 
this genus in Porto Rico and in Jamaica, and have arrived at con- 
clusions that are, to us, more satisfactory as to the number of spe- 
cies that are represented in the West Indian waters, in so far as 
one may judge of the matter from the material now at hand. We 
therefore venture to give below a diagnosis of the genus, a key to 
the American species, and a synoptical account of the four species 
that we recognize. 
AVRAINVILLEA Decaisne, Ann. Sci. Nat. II]. 18: 108. 1842 
Fradelia Chauvin, Recherches 124. 1842. 
Chloroplegma Zanard, Mem. R. Ist. Ven.'7: 290. 1858. 
Thallus fusco-nigrescent, tawny-green, or olivaceous, usually 
flabelliform and stipitate, more rarely difform or irregularly dig 
tate, destitute of calcareous incrustation, composed of dichotomous 
interwoven cylindrical, torulose, or moniliform threads, these nearly 
similar throughout, being without specialized corticating branches 
and without fibular processes. Stipe, when differentiated, simple 
or sometimes forked, terete or flattened. Flabellum suborbicular, 
reniform-cordate, or cuneiform, or (in A. Rawsont) deficient, r arely 
zonate. Rhizoids in an irregularly bulbous mass or sometimes 
forming a rhizome. Sporangia (known only in A, nigricans) ter- 
minal on filaments exserted from surface of flabellum, containing 4 
few (1-8) spores (aplanospores?), All species marine. 
Type species, Avrainvillea nigricans Decaisne. 
Key to the American species 
Thallus eventually developing a flabellum (usually stipitate). 
Sco-nigrescent or tawny-green; surface subvelutinous, minutely spongiose, “ 
strigose : filaments of flabellum 28-70 4 in diameter. 
Filaments of flabellum moniliform. 1. A. nigricans. 
Filaments of flabellum cylindrical with a strong constriction at base of each 
branch, rarely subtorulose. 2. A. longicaults 
Olivaceous or cinereous ; surface smooth and compact ; filaments of surface 
flabellum 6-24 in diameter, . A, levis. : 
Thallus not developing a flabellum, forming more or less digitate, sometimes capitate 
lobes, these commonly very irregular in form, and often branching, diffluent, - 
: 3 Ae 
anastomosing qwsont. 
I. AVRAINVILLEA NIGRICANS Descaisne, Ann, Sci. Nat. Il. 18+ 
1842.— M. A. Howe, Bull. Torrey Club 32: 567, 568. 1.905: 
' Fradelia fuliginosa Chauvin, Recherches 124. 1842. 
