elegantly nru-sliaped. Tetraspores forming a row in tlie upper half of the
ultimate ramuli, and generally extending to the apex. Colour a full, deep
red, becoming much darker, and even black in drying. Substance rigid,
not strongly adhering to paper.
Polysiphonia urceolata is subject to some minor variations,
according to the locality in- which it grows. When found on
rocks, in exposed situations, near low-water mark, the filaments
are more robust, of greater length, and much more branching;
these constitute the typical form of the species, as restricted by
Agardh. When growing on the stems of Laminaria digitata
the filaments are much less branched, the lateral branches shorter,
and the ramuli remarkably squarrose, often hooked backwards.
Such specimens constitute the P. patens of Agardh, and are well
represented in Lyngbye’s figure quoted above. To the naked
eye the extreme states of these two varieties are sufficiently
characterised, but various intermediate forms insensibly connect
them, and I have found it impossible to discover any satisfactory
distinction between them. The Conferva patens of Dillwyn
appears to be merely the young state of the plant.
A
Fig. l._ P o ly s ip h o n i a u r c e o l a t a ; t u f t 0/ natural size. 3. Branch
with capsules. 3. A capsule, 4. Branch with tetraspores. 5. Baiuulus
from the same. 6. A tetraspore. 7. Portion of a branch and ramulus,
to show the comparative length of the joints. 8. Portion of the lower part
of the stem, to show the same. 9. Cross-section of a filament;—all
more or less highly magnified.
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