
SEA-WEEDS. 233 
most delicate of the genus, may be sought; and several Pho- 
domele, very beautiful, blackish-red, feathery, and tufted 
sea-weeds beside, not forgetting the Polysiphonie of many 
forms and sizes, the most common, perhaps, and to me the 
most interesting, being the blackish one, which grows in 
tufts on fuci, the P. fastigiata; others, far more delicate and 
of more pleasing colors, likewise occur with us; and with 
them the Bostrychia rivulsari also southern in its habits as a 
genus, and the beautiful Dasya, more at home farther south, 
is often met with in collections of Algæ gathered hereabouts, 
D. Elegans being one of the comparatively sparse Alge on 
the sandy shores of Nantucket. 
Tn the order Lawrencrace& the fronds are terete or com- 
pressed, rarely flattened, the seeds contained in external 
globose conceptacles, the tetraspores immersed in various 
parts of the frond. There is much diversity in the color of 
the several species; usually, however, a lurid purple is the 
typical one, fading on exposure to the light, and parting 
with it readily on being immersed in fresh water. The 
Laurencias, on which the order is founded, are southern, but 
Champia occurs at Providence, R. I., at Nantucket, and 
New York, and may be sought as a parasitical plant farther 
north. 
: The Srmærococcomreæ embrace a vast number of very 
interesting sea-weeds, mostly resident in tropical and foreign 
Seas. I know of none whose structure has interested me 
more, and if any species occur to the reader on our shores, in 
© few which may be sought here, they will afford rare 
gratification with the microscope, their internal structure 
varying as much as the outward forms. Some of the finest 
and most brilliant weeds are to be found, a few only are of a 
duller'tint, The seeds are lodged in elegantly formed con- 
: “eptacles, which are filled with beaded filaments, on. the 
2 Te of which the seeds are situated; the tetraspores are In 
te groups, or else dispersed over the whole fronds. ' 
“he DELESSERTÆ have rosy-red, leaf-like, branched, jag- 
AER; NATURALIST, VOL. II. 30 

