30 
the filaments only rather seldom constricted above the dichotomy and 
by its thin walls. But it seems to me that these differences may 
very possibly be ascribed to the rather great depth at which the 
plant was found. 
Avrainvillea nigricans Decaisne. 
Decaisne, Sur les Corallines etc. (l.c. p. 108). Howe, Phy- 
cological Studies III (1. c. p.508). Avr. nigricans Decsne., Murray 
and Boodle 1. c. p. 70, the specimens from ‘Iles des Saintes prope 
la Guadeloupe, d’Avrainville’. Avr. longicaulis Murray and Boodle, 
I. c. excluding syn. Rhipilia longicaulis Kütz. Avr. sordida Murray 
and Boodle, 1. c. at all events the Nr. 174 bis, which I have been 
able to examine through the kindness of Dr. Bornet and which 
contains only rather small, but to be sure, quite characteristic spe- 
cimens of this species). 
This species is characterized by its very regularly moniliform 
fllaments, those of the interior being thicker, more often varying 
to both sides of 50 w (Fig. 2 6, c); while those of the surface grow 
thinner, about 30 y and get shorter links (Fig. 2a). These fila- 
ments are woven together forming a very loose and open cortical 
layer. 
The chromatophores are spindleshaped and contain a pyrenoid 
(Fig. 2c); much amylum is to be found, especially in the older 
filaments. 
Avr. nigricans has a rather heterogeneous habitus. The stipe, 
which takes its rise from a terete rhizome lying on the bottom, is 
terete, though often flattened in the uppermost part, passing evenly 
into the flabellum; the stipe can be 10—15 cm. longand even more, 
or quite short. The shape of the flabellum also varies much. It 
can be transverse, oval or reniform, often with cordate or cuneiform 
base, with the margin entire, or more or less lacerated, or even 
lobed. Most commonly it is not at all zonate, but specimens also 
occur which are very clearly zonate. 
On account of the very loose texture of the flabellum Avr. 
1) As Dr. A. Gepp most kindly informs me only the Nr. 30 of Mazé, 
Algues de Guadeloupe is the type of Avr. sordida Crn. 
