ALGÆ ANTARCTIC. 269 
cavum radiatim cingentibus formata.  Keramidia...... 
Stichidia lanceolata ramulos terminantia, tetrasporas plu- 
riseriatas includentia.—Alge  pusille cæspitosæ e filis 
repentibus orte, rupes marinas Antillanas, Antarcticas et 
Austro-Atlanticas, vix demersas, vel ad limitem pleni maris 
cestus sitas, incolentes. 
A very natural little group, which occupies in the Southern 
Ocean the same position with respect ‘to high-water mark 
that Lichina and Catenella do in the Northern. 
48. Bostrychia Hookeri, Harv.; caulibus indivisis apice 
involufis, ramis lateralibus abbreviatis alternis subquadri- 
fariis erecto-patentibus, inferioribus subulatis simplicibus 
furcatisve, superioribus alterné multifidis, ramulis subu- 
latis acutis erectis, axillis angustis acutis, stictis sub- 
triseriatis, stichidiis lanceolatis acutis ramulos minores 
terminantibus. 
Has. Cape Horn and the Falkland Islands. 
Fronds 1-1i inches high, densely tufted, blackish-purple, 
rigid. Stem generally undivided, furnished with lateral 
short branches throughout its length. Branches sometimes 
all about a line long, and but slightly divided; some- 
times the lowest are ofthis length and character, the upper 
2-4 lines long, and repeatedly branched. All the ramuli 
are subulate and erect, or erecto-patent. The tips of the 
stem and main branches are generally strongly involute. 
Under the microscope the branches and ramuli appear beau- 
tifully marked with three rows of dark purple dot-like cells. 
49. Bostrychia fastigiata, nobis; caulibus multifidis fastigiatis 
apicibus involutis, ramis equilongis curvatis, ramulis. 
formia seriem duplicem sphærosporarum includentia ; 29. concep- 
tacula pedicellata sporis clavatis erectis referta."— Hist. Nat. 
de Cuba, 
We are unable to find the “ fila elongata colorata," filling the axis. 
On the contrary, in the species now described, as well as in B. radicans, 
Mont, the axis is a tube, interrupted at intervals by membranous 
diaphragms. The structure is indeed very similar to that of Polysiphonia, 
from which this genus differs in having the cellules of the periphery very 
short, while those constituting the axis are lengthened. 
