foil j'ri r i i í i
r a
short distances asunder (revealing the joints of the internal axis), and the
whole surface is reticulated with anastomosing cells. Fructijication: 1,
Ceramidia, densely crowded on the ramuli, ovate, sessüe; rarely produced;
2, tetraspores imbedded in the multifid, lateral ramuli. Suhstance cartilaginous
and firm, the tips of the branches standing out, and each retaining
a drop of water when the specimen is lifted into air. Colour a dark purple,
changing into olive green, and finaly to amber-yellow under the infiuence
of sunlight. .___________________ _
I have always thought that in whatever genus we put Byti-
phlfsa complanata of Agardh, in the same we must place not only
the Polysiphonia thuyoides of British authors, hvX P . fruticulosa
also. The internal structure of these plants is identical. They
all possess a central jomted axis composed of many tubes, like
the frond of Polysiphonia, coated on the outside by a broad band
of small irregular cells. The surface appears reticulated under
the microscope, and marked at short intervals by dark-coloured
transverse lines. These characters belong to the frond of Byti-
phlata, in which genus Agardh places the first of the three plants
in question ; while both the latter have hitherto been referred to
Polysiphonia. As I have already (PI. CLXX.) adopted Agardh’s
name for the former, I am now constrained to alter the position
of the two latter, and transfer them from Polysiphonia to
Bytiphlma. These three plants have not only a similar structure,
but have so much the same natural habit, that specimens may be
found which bring them inconveniently near each other. Some
specimens of B. fruticulosa are very close to some of B. thuyoides,
and the latter, in like manner, closely approaches narrow states
of B. complanata. So nearly do they approach, that at one time
I regarded them all as merely sportive forms of one species, but
this was before I had much opportunity of studying them in a
living state. When growing, each possesses characters sufficiently
obvious. It is only in a few cases of imperfect or badly
dried specimens that the student will find it difficult to decide
to which species the specimen should be referred.
The ceramidia of this species are not often found, but when
they occur they are generally formed in profusion, almost every
twig bearing one or two. They are always borne on less luxuriant
specimens than those which yield tetraspores.
Pig. 1. R y t i p h l æ a f r u t i c u l o s a :—o f the natural size. 2. Small brancli with
ceramidia. 3. A ceramidium in situ. 4. Small branch from another plant.
5. Ramulus with imbedded tetraspores. 6. Tetraspore. 7. Portion of the
stem. Section of the same ;— all more or It